(L  d 


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X  >4^-0~A 


ELEMENTS 

OF 

MINERALOGY,  CRYSTALLOGRAPHY 

AND 

BLOWPIPE  ANALYSIS 

FROM  A   PRACTICAL  STANDPOINT 


A  DESCRIPTION  OF  ALL  COMMON  OR  USEFUL  MINERALS,  THE 

TESTS    NECESSARY    FOR    THEIR    IDENTIFICATION,    THE 

RECOGNITION  AND  MEASUREMENT  OF  THEIR 

CRYSTALS,  AND  A  CONCISE  STATEMENT 

OF  THEIR   USES  IN  THE  ARTS 


ALFRED    J.  MOSES,  E.M.,  PH.D. 

Professor  of  Mineralogy,  Columbia  University,  New  York  City 
AND 

CHARLES   LATHROP    PARSONS,  B.S. 

Professor  of  General  and  Analytical  Chemistry,  New  Hampshire  College,  Durham,  N.  H. 


THIRD   ENLARGED   EDITION 

PART  I  REWRITTEN.      PARTS  II,   III  AND  IV  EXTENSIVELY  REVISED 
WITH  583  FIGURES  AND  448  PAGES  OF  TEXT 


NEW  YORK 

D.  VAN   NOSTRAND    COMPANY 
1906 


Entered  according  to  the  Act  of  Congress  in  the  year  1904,  by 

A.  J.  MOSES  AND  C.  L.  PARSONS 
In  the  Office  of  the  Librarian  of  Congress.     All  rights  reserved. 


Geol. 
Ub. 


PREFACE. 

In  this  edition  of  our  text-book  we  have  adhered  to  the  design 
of  the  editions  of  1895  and  1900,  to  present  the  facts  leading  to  a 
useful  knowledge  of  mineralogy  in  such  a  manner  that  the  student 
in  the  technical  school  and  the  professional  man  in  the  field  may 
readily  learn  to  recognize  or,  when  necessary,  to  determine  all  im- 
portant minerals. 

We  have  made  a  number  of  changes  and  additions  which  ex- 
perience has  shown  to  be  desirable.  Some  of  these  are  : 

Part  I.,  Crystallography,  has  been  entirely  rewritten  and  the 
attempt  has  been  made  to  subordinate  the  study  of  models  to  the 
study  of  actual  crystals. 

The  introductory  portion  of  Part  III.,  Descriptive  Mineralogy, 
has  been  carefully  revised  and  rewritten,  a  chapter  added  upon  "  Oc- 
currence and  Origin  of  Minerals  ";  the  discussion  of  chemical  com- 
position and  chemical  relations  of  minerals  made  more  thorough  ; 
the  optical  portion  simplified  and  the  phenomena  of  radioactivity, 
fluorescence  and  phosphorescence  described. 

In  the  descriptions  of  species  the  statistics  and  methods  of  pro- 
duction have  been  brought  down  to  date,  the  lithium  minerals 
assembled,  and  the  carbon  minerals  elaborated.  A  few  economic 
species  have  been  added,  a  few  rare  species  omitted  and  the  de- 
scriptions of  species  of  minor  importance  condensed. 

A  number  of  half-tones  have  been  added  and  in  the  crystallo- 
graphic  discussions  the  supplement  angles  have  been  used. 


TABLE   OF   CONTENTS. 


PART  I. — CRYSTALLOGRAPHY.     CHAPTERS  I.  TO  IX.,  PAGES 
i  TO  74. 

Chapter            I.      Introductory 1-22 

Chapter          II.     The  Triclinic  System 23— 25 

Chapter        III.     The  Monoclinic  System 26-29 

Chapter         IV.     The  Orthorhombic  System 3°~35 

Chapter          V.     The  Tetragonal  System  36-4 1 

Chapter         VI.     The  Hexagonal  System  42-51 

Chapter       VII.     The  Isometric  System 52—60 

Chapter     VIII.     Twin  Crystals  or  Macles 61-66 

Chapter         IX.     Crystal  Drawing  and  Graphic  Solution 

of  Stereographic  Projections 6 7-74 

PART  II.  — BLOWPIPE  ANALYSIS.     CHAPTERS   X.   TO   XIII., 
PAGES  75  TO  127. 

Chapter          X.     Apparatus  Blast,   Flame,  etc 75~8i 

Chapter         XI.      Operations  of  Blowpipe  Analysis 82—101 

Chapter       XII.      Summary   of    Useful    Tests   with    the 

Blowpipe  102-116 

Chapter      XIII.     Schemes     for     Qualitative     Blowpipe 

Analysis  1 1 7-1 2  7 

PART  III. — DESCRIPTIVE  MINERALOGY.     CHAPTERS  XIV.  TO 
XXXVI.,  PAGES  128  TO  424. 

Chapter      XIV.     Descriptive  Terms  128-142 

Chapter  XV.  Characters  Dependent  on  Cohesion 

and  General  Characters 143-153 

Chapter  XVI.  The  Optical  Characters  which  are 

Observed  by  Common  Light 154-160 

Chapter  XVII.  The  Optical  Characters  Obtained  with 

Polarized  Light  161-176 

Chapter  XVIII.  The  Thermal,  Magnetic  and  Electrical 

Characters  177-180 

Chapter     XIX.     Chemical  Composition  and  Reactions  181-190 

Chapter  XX.  The  Occurrence  and  Origin  of  Min- 
erals   191-205 


TABLE    OF   CONTEXTS. 


PART  III.  — DESCRIPTIVE  MINERALOGY —  Continued. 

Chapter        XXI.     The  Iron  Minerals    206-226 

Chapter       XXII.     The  Manganese  Minerals 227-232 

Chapter     XXIII.     Nickel  and  Cobalt  Minerals 233-240 

The  Cobalt  Minerals 233 

The  Nickel  Minerals 236 

Chapter     XXIV.     Zinc  and  Cadmium  Minerals 241-247 

The  Zinc  Minerals 241 

The  Cadmium  Minerals 246 

Chapter       XXV.     Tin,  Titanium  and  Thorium  Minerals.    248-254 

The  Tin  Minerals 248 

The  Titanium  Minerals 250 

The  Thorium  Minerals 252 

Chapter      XXVI.     Lead  and  Bismuth  Minerals 255-269 

The  Lead  Minerals  255 

The  Bismuth  Minerals 266 

Chapter    XXVII.     Arsenic,     Antimony,    Uranium    and 

Molybdenum  Minerals 270—278 

The  Arsenic  Minerals  270 

The  Antimony  Minerals  ...   272 

The  Uranium  Minerals 275 

The  Molybdenum  Minerals  277 

Chapter  XXVIII.     The  Copper  Minerals 279-292 

Chapter     XXIX.     Mercury  and  Silver  Minerals 293-302 

The  Mercury  Minerals 293 

The  Silver  Minerals 295 

Chapter       XXX.     Gold,    Platinum   and   Iridium    Min- 
erals     303—308 

The  Gold  Minerals 303 

The  Platinum  and  Iridium  Min- 
erals     307 

Chapter     XXXI.     Potassium,  Sodium,  Lithium  and  Am- 
monium Minerals 309—318 

The  Potassium  Minerals  ...   309 

The  Sodium  Minerals  311 

The  Lithium  Minerals 315 

The  Ammonium  Minerals..  317 

Chapter   XXXII.     Barium  and  Strontium  Minerals 319-323 

The  Barium  Minerals 319 

The  Strontium  Minerals  ...   321 

Chapter  XXXIII.     Calcium  and  Magnesium  Minerals  ...   324-342 

The  Calcium  Minerals 324 

The  Magnesium  Minerals....  339 


TABLE    OF  CONTENTS.  vii 

PART  III. — DESCRIPTIVE  MINERALOGY. —  Continued. 

Chapter  XXXIV.     The  Aluminum  Minerals 343~354 

Chapter    XXXV.     Boron,  Sulphur,  Tellurium,  Hydrogen 

and  Carbon  Minerals 355-369 

The  Boron  Minerals 355 

The  Sulphur  and  Tellurium 

Minerals 359 

The  Hydrogen  Minerals,  ..361 

The  Carbon  Minerals  362 

Chapter  XXXVI.     Silica  and  the  Silicates 369-424 

Silica 372 

Polysilicates 377 

Metasilicates 383 

Orthosilicates 394 

Basic  or  Subsilicates 409 

Hydrous  Silicates 412 

Titano-Silicates 424 

PART  IV. — DETERMINATIVE  MINERALOGY.     PAGES  425 
TO  427  AND  INSETS. 

Chapter  XXXVII.  Tables    for  Rapid    Determination  of 

the  Common  Minerals 425 

I.   Minerals  of  Metallic  or  Subme- 

tallic  Lustre. 
II.   Minerals  of  Non-Metallic  Lustre. 

A.  With  Decided  Tastes,  that  is 

Soluble  in  Water. 

B.  Without   Taste,    but  yielding 

Coating  or  Magnetic  Residue 
when  Heated  on  Charcoal. 

C.  Tasteless,     Non-volatile     and 

NOT    made    Magnetic   by 
Heating  on  Charcoal. 
Table  of  Atomic  Weights 427 

GENERAL  INDEX 428-438 

INDEX  TO  MINERALS 438-443 


PART  I. 


CRYSTALLOGRAPHY. 


CHAPTER   I. 

INTRODUCTORY. 

Solidification  of  Chemical  Substances. 

When  a  homogeneous  substance,  for  which  a  chemical  formula 
can  be  written,  passes  from  the  liquid  or  gaseous  state  or  separates 
from  solution  there  usually  form  distinct  individual  solids  which 
are  bounded  by  plane  faces,  and  possess  a  certain  constancy  in 
shape,  which  is  characteristic  of  the  substance. 
Crystals  and  Crystallization. 

These  solids  are  called  "crystals"  and  their  formation  is  called 
crystallization.  It  may  therefore  be  said  that: 

(a)  CRYSTALS*  are  solids  formed  only  when  a  chemical  element 
or  a  chemical  compound  solidifies.  They  are  bounded  by  plane 
faces  at  definite  angles  to  each  other  which  are  characteristic  of 
the  substance. 

(&}  CRYSTALLIZATION  is  the  solidification  of  a  chemical  element 
or  compound  and  must  result  either  in  distinct  crystals  or  in 
crystal  aggregates,  that  is,  masses  of  crystals  which  have  been 
hindered  in  development  by  lack  of  space,  or  time  or  other  cause. 
Crystal  Structure. 

Disregarding  the  question  of  the  nature  of  the  smallest  solid 
particles  of  matter,  about  which  little  is  known,  the  geometric  forms 
of  the  crystals  and  many  of  their  physical  characters  prove  a 
homogeneous  structure,  that  is,  each  particle  is  in  a  similar  position 


*  The  term  crystal  or  rock  crystal  has  been  used  for  over  two  thousand  years  as  a 
name  for  the  substance  silica  when  found  in  colorless  angular  forms.  Certain  clear 
varieties  of  glass  are  also  known  as  crystal. 


2  CR  YSTALL  OGRAPHY. 

with  respect  to  those  surrounding  it ;  each  is  the  center  of  a 
precisely  similar  group,  and  along  any  line,  and  all  parallel  lines, 
the  particles  are  equally  far  apart. 

Such  a  structure  is  illustrated  in 
Fig.  i,  the  particle  O  is  surrounded 
by  six  similar  particles  A,  B,  C,  D,  E 
and  F  at  fixed  distances  OA  =  OB, 
OC=OD  and  OE  =  OF.  Each  of 
^  the  six  is  itself  the  center  of  a  simi- 

~^  lar  group,  the  intervals  in  the  same 
direction  being  as  before,  that  is 
AH  =  OA,  CL  =  OC,  EK=  OEand 
so  on.  Different  substances  differ  in 
the  grouping  of  their  particles  so  that 

each  has  its  own  characteristic  crystals.  All  this  has  been  theo- 
retically considered  and  the  possible  variation  of  regular  grouping 
discussed.* 

Regular  Structure  in  Absence  of  Distinct  Crystals. 

In  the  solidification  of  chemical  compounds  a  regular  arrangement 
of  the  particles  takes  place  whether  distinct  crystals  are  formed  or 
not.  This  can  be  proved  in  many  ways  ;  for  instance, 

(a)  The  masses  will  often  break  in  directions  parallel  to  planes 
yielding  solids  absolutely  constant  in  angles,  and  these  solids  can 
be  broken  from  any  part  of  the  mass  and  of  any  size. 

(£)  The  velocity  of  transmission  f  of  light,  is  the  same  along 
all  parallel  lines,  but  is  not  generally  the  same  along  lines  not 
parallel. 

(<:)  The  same  constancy  for  parallel  lines  and  variation  for  lines 
not  parallel  is  shown  for  other  physical  characters  such  as  expan- 
sion from  heat,  conductivity  of  heat  or  electricity,  and  even  color 
and  luster. 

Summation  of  Preceding  Paragraphs. 

The  important  points  thus  far  stated  are  : 

I.  That  the  solidification  of  chemical   substances  is  a  regular 

*See  Report  of  Committee  "On  Structure  of  Crystals, "  Proc.  Roy.  Soc.,  Section  C, 
Glasgow,  1901,  for  a  general  review. 

f  In  glass  or  other  homogeneous  solids  which  are  not  definite  chemical  compounds 
the  velocity  of  transmission  is,  generally  speaking,  the  same  in  all  directions,  or  if 
unlike  it  is  without  any  regularity  of  difference. 


INTRODUCTORY.  3 

arrangement  of  the  minutest  solid  particles  in  straight  lines  and 
planes  so  that  each  particle  is  the  center  of  a  precisely  similar 
group  of  particles. 

2.  That   the    solidification    often    results   in    the  formation  of 
polyedral  solids  called  crystals. 

3.  That  different  chemical  substances  have  different  structures, 
and  the  resultant  crystals  are  not  alike  in  shape. 

4.  That  the  shapes  of  the  crystals  characterize  the  substance. 

The  Angles  of  Crystals. 

In  any  polyedron  three  sorts  of  angles  exist. 

1.  Plane  angles  between  the  intersections  of  faces.     These  are 
little  used. 

2.  Interfacial  or  diedral  angles.     These  are  the  most  important. 

3.  Corners  or  polyedral  angles  between  three  or  more  planes. 

Law  of  Constancy  of  Interfacial  Angles. 

The  angles  of  crystals  of  any  one  substance  conform  to  the  fol- 
lowing law  :  In  all  crystals  of  the  same  substance  the  angles  between 
corresponding  faces  are  constant* 

Figs.  2  and  5  represent  actual  crystals  of  quartz.      Figs.  3  and 

FIGS.  2-7. 


•6  are  sections  of  these  in  the  direction  of  the  plane  of  the  paper 
which  show   that   the  angles    between  corresponding   faces  are 

*Steno  in  1669  announced  that  in  rock  crystal  there  was  no  variation  of  angle  in 
spite  of  the  variation  in  relative  size  of  the  faces. 

Rome  Delisle  in  1783  measured  and  described  over  four  hundred  crystal  forms  and 
announced  that  in  each  species  "the  respective  inclination  of  the  faces  to  each  other 
never  varies." 


CR  YSTALL  OGRAPHY. 


FIG. 


equal.     The  same  is  shown  by  sections  at  right  angles  to  the 
paper,  Figs.  4  and  7. 

Similarly  in  Fig.  8  the  faces  of  the  mag- 
netite crystal  are  exactly  parallel  to  those 
of  the  octahedron  represented  within  it,  that 
is,  such  crystals  of  magnetite  are  bounded 
by  faces  which  may  or  may  not  be  equal 
in  size  but  in  which  the  angle  between  ad- 
jacent faces  is  109°  28'  16". 

THE   APPROXIMATE   MEASUREMENT   OF   INTERFACIAL 
ANGLES. 

Measurements  within  one  or  two  degrees  may  be  made  with 
Contact  goniometers,  the  most  simple  type  of  which  consist  of  an 
arm  pivoted  upon  a  protractor.  Fig.  9  shows  such  an  instrument 

FIG.  9. 


consisting  of  a  cardboard  on  which  is  printed  a  semicircle  gradu- 
ated from  o°  to  1 80°  in  both  directions. 

An  arm  of  transparent  celluloid  is  swivelled  by  means  of  an  eyelet 
exactly  in  the  center  of  the  semicircle  tightly  enough  to  turn  with 
some  difficulty. 

In  measuring,  the  crystal  or  model  is  placed  as  shown  so  that 
the  card  edge  and  swinging  arm  are  each  perpendicular  to  the  edge 
of  intersection  of  the  two  faces,  and  in  such  close  contact  that  no 
light  passes  between  the  arms  and  the  faces. 


INTR  OD  UCTOR  Y.  5 

Either  the  actual  angle  or  its  supplement  may  be  read  upon  the 
scale.* 

A  more  expensive  instrument,  Fig.  10,  consists  of  a  brass  pro- 
tractor with  detachable  arms  which  can  be  slid  upon  the  pivot  until 
of  the  most  convenient  length 
for  the  particular  crystal.  FlG-  I0- 

In  measuring  it  is  conven- 
ient to  set  the  arms  at  an 
angle  a  little  less  than  the 
angle  to  be  measured,  clamp 
loosely  and  make  the  fine 
adjustment  by  placing  one  of 
the  arms  in  perfect  contact 
with  one  crystal  face,  the  other 
arm  nearly  touching  the  sec- 
ond face  and,  while  holding 
between  the  eye  and  the  light, 

to  bring  the  second  arm  into  perfect  parallelism  with  the  second 
face  by  a  gentle  pressure  with  the  forefinger. 

The  arms  are  then  replaced  on  the  arc,  as  in  the  figure,  and  the 
angle  is  read.  In  the  figure  the  angle  is  120°. 

Three  measurements  should  be  made  and  the  average  should  be 
correct  within  one  degree.      After  each  reading  the  arm  should  be 
undamped  and  the  new  measurement  made  as  if  it  were  a  different 
angle. 
The  Two-Circle  Contact  Goniometer. 

A  convenient  instrument  f  for  finding  both  the  symmetry  and 
the  crystal  angles  is  shown  in  Fig.  1 1 .  The  crystal  is  fastened 
with  wax  to  the  carrier  /  which  permits  some  adjustment..  The  rod 
R  passes  radially  through  the  movable  arc  A  and  can  be  pushed 
in  and  out  or  turned.  The  knife  edge  k  is  at  right  angles  to  R 
and  therefore  when  R  is  turned  the  edge  k  is  always  a  line  of  a 
plane  perpendicular  to  a  radius. 

To  adjust  the  crystal  with  any  zone  %  vertical  the  arc  A  is  moved 

*  This  instrument  called  the  Penfield  Goniometer,  Model  B,  can  be  purchased  from 
dealers  at  50  cents. 

t  Goldschmidt's  Zweikreisiges  Anlege-Goniometer  made  by  Peter  Stoe  of  Heidelberg 
at  32  marks. 

J  A  zone  is  a  series  of  planes  parallel  to  the  same  line  ;  intersections  of  these  planes 
are  parallel  to  this  line  and  to  each  other.  In  the  case  of  quartz  after  adjustment  a  vertical 
and  oblique  face  would  probably  be  read  alternately  as  this  could  be  done  more  quickly. 


6  CRYSTALLOGRAPHY. 

to  90°  on  the  vertical  circle  Fand  the  faces  of  the  zone  are  suc- 
cessively brought  by  rotation  of  the  horizontal  circle  to  coincide 
with  the  revolved  knife  edge  k,  that  is  they  are  made  perpendicular 
to  a  horizontal  radius  and  therefore  vertical. 

The  measurement  thereafter  proceeds  as  follows : 

The  horizontal  circle  H  is  revolved  until  each  of  the  faces  of  the 


FJC; 


vertical  zone  has  been  made  to  coincide  with  the  horizontally  placed 
knife  edge  k.  The  successive  readings  are  noted  on  the  horizontal 
circle. 

The  arc  A  is  then  slid  along  the  vertical  circle  Fand  the  horizontal 
circle  //"is  turned  until  positions  are  found  for  which  the  knife  edge 
during  a  revolution  coincides  with  an  oblique  face. 

If  one  of  the  readings  on  the  horizontal  circle  H  is  taken  as  an 
origin  then  the  differences  between  this  and  the  readings  for  the 
other  faces  yield  angles  which  may  be  denoted  by  <f>,  the  corre- 
sponding readings  on  the  vertical  circle  V  being  denoted  by  p. 

If  the  crystal  shown  in  the  figure  is  quartz,  there  would  result 
for  the  six  vertical  faces  one  common  value  p  =  90°  and  for  <p 
successive  values  o°,  60°,  120°,  180°,  240°,  300°,  and  for  the 
oblique  faces  the  values  would  be  constant  for  p  =  52°  approx. 
and  for  <p  =  o°,  60°,  120°,  180°,  240°,  300°. 


INTR  OD  UCTOR  Y.  J 

Miller's  Substitute  for  a  Reflection  Goniometer. 

When  the  crystal  has  bright  faces  which  are  too  small  for  the 
application  goniometer  the  crystal  angles  may  be  measured  within 
one  degree  by  an  apparatus  consisting  (Fig.  1 2)  simply  of  a  small 
rectangular  strip  of  wood  say  3"x  i"x  y^"  into  which  has  been 

FIG.  12. 


set  perpendicularly  a  stiff  wire  about  3"  long,  one  end  of  which  is 
pointed  and  protrudes  slightly  on  the  under  side  to  serve  as  a 
pivot,  the  other  end  is  flat.  The  crystal  is  attached  by  wax  with 
the  edge  to  be  parallel  to  the  length  of  the  wire.  The  apparatus 
is  then  placed  upon  a  fixed  sheet  of  paper  on  a  horizontal  surface, 
the  eye  is  brought  close  to  the  crystal  and  the  apparatus  turned  on 
its  pivot  until  the  image  of  some  distant  object  reflected  from  the 
face  is  seen  coincident  with  some  near  vertical  line  such  as  the  edge 
of  a  window  frame. 

A  line  is  then  ruled  on  the  paper  along  the  edge  of  the  wooden 
base,  and  the  apparatus  is  again  turned  until  the  same  distant  object 
is  seen  reflected  from  the  second  face  coincident  with  the  same 
vertical  line.  A  second  line  is  ruled  on  the  paper  along  the  edge 
of  the  base  and  the  angle  between  these  two  ruled  lines  is  measured 
by  a  protractor  and  is  the  supplement  angle  between  the  two  faces. 

THE  ACCURATE*  MEASUREMENT  OF  INTERFACIAL  ANGLES. 
The  angles  between  smooth  bright  faces  can  be  measured  to 
half  minutes  or  even  closer,  as  follows  : 


*The  fundamental  necessity  for  good  measurement  is  a  good  crystal  with  bright 
smooth  faces.     This  is  more  apt  to  be  found  among  little  crystals  than  large  ones. 


8 


CR  YSTALLOGRAPHY. 


The  crystal  is  adjusted  so  that  an  edge  coincides  with  the  axis 
of  rotation  O,  Fig.  13.  CO  is  a  ray  of  light  fixed  in  direction. 
OTis  the  line  of  sight.  NO  bisects  the  angle  COT. 

Whatever  the  position  of 
the  crystal  the  ray  CO  strik- 
ing it  is  reflected.  But 
only  when  a  face  of  the  cry- 
stal coincides  with  a  plane 
through  AB'  at  right  angles 
to  NO,  and  through  the 
axis  of  rotation,  can  the 
reflection  follow  the  line 
OT.  For  a  position  of 
the  crystal  indicated  by  the 
black  rhomb,  one  face  coin- 
cides with  AB' ,  and  a  re- 
flection reaches  T.  Another 
face  at  that  time  coincides 
with  OB.  A  reflection  will  be  obtained  from  this  second  face, 
after  a  rotation  measured  by  the  arc  BB' ,  the  supplement  of  the 
arc  AB,  which  measures  the  angle  between  the  faces. 

The  axis  of  rotation  may  be  horizontal  or  vertical.  For  most 
work  the  latter  is  preferable. 

Fig.    14  shows  the  simplest  form  of  the   Fuess  goniometer  * 
(Model  4,  a)  which  is  admirably  adapted  for  student  work. 
Two  telescopes  are  used  : 

(a)  The  collimator  telescope  C  is  fixed  in  position  and  guides  to 
the  crystal  a  ray  of  light  from  a  lamp  set  at  the  outer  end.  At 
this  end  is  an  orifice  like  a  double  crescent,  Fig.  1 5,  formed  by  two 
circular  discs  of  equal  diameter  set  a  distance  apart  which  can  be 
regulated  by  a  screw. 

(b}  The  observation  telescope  T,  may  be  set  at  any  angle  to  C, 
the  axes  of  T  and  C  always  remaining  in  a  horizontal  plane  and 
intersecting  in  the  axis  of  rotation.  Within  T  are  two  cross  hairs, 
one  vertical,  the  other  horizontal. 

Before  the  objective  swings  an  extra  lens  which,  when  down,  con- 
verts the  telescope  into  a  weak  microscope,  and  brings  the  crystal 
into  focus.  When  it  is  raised  the  telescope  is  focused  upon  the  light. 


*  R.  Fuess,  Steglitz,  near  Berlin,  marks  260,  or  about  65  dollars. 


INTR  OD  UCTOR  Y.  9 

The  crystal  carrier  is  shown  between  the  telescopes. 
Adjusting  the  Crystal. 

The  crystal  is  carefully  cleaned  with  alcohol  and  chamois  skin 
and  thereafter  handled  only  with  forceps.  It  is  attached  by  wax 
to  the  plate  p  as  nearly  as  possible  in  the  correct  position.  One 
of  the  faces  of  the  angle  to  be  measured  is  placed  approximately 
parallel  to  one  of  the  sliding  screws,  for  instance  ;/,  and  that  screw 
is  placed  at  right  angles  to  the  telescope. 

The  extra  lens  is  dropped  and  the  crystal  raised  or  lowered  into 
the  field  by  loosening  the  screw  d.  The  edge  is  then  moved  by ;/ 

FIG.   14. 


and  tipped  by  the  screw  k  of  the  corresponding  circular  arc  until 
it  appears  to  coincide  with  the  vertical  cross  hair.  The  screw  a 
is  then  loosened  and  the  crystal  turned  90°  by  the  pilot  wheel  / 
and  the  edge  is  in  turn  moved  by  o  and  tipped  by  the  other  cir- 
cular arc  into  apparent  coincidence  with  the  vertical  cross  hair. 
This  is  repeated  by  turning  back  90°  until  during  a  rotation  the 
edge  and  cross  hair  appear  to  coincide. 

The  extra  lens  is  then  raised  and  if  the  images  of  the  signal  from 
the  faces  can  be  bisected  by  the  cross  hairs  as  in  Fig.  1 5  the  ad- 
justment is  satisfactory. 


10 


CR  YSTALLOGRAPHY. 


The  Measuring. 


FIG.  15. 


The  screw  G  is  loosened  and  the  tele- 
scope set  at  some  convenient  angle  to  the 
collimator  (100  to  120  degrees).  The 
screw  a  is  then  loosened,  the  graduated 
circle  and  crystal  are  turned  together  by 
the  pilot-wheel/,  until  the  reflected  signal 
is  seen  through  the  telescope,  then  a  is 
tightened,  the  signal  moved  by  the  tan- 
gent screw  F  until  it  is  bisected  by  the 
vertical  cross  hair,  as  in  Fig.  15,  and 
the  vernier  is  read  and  recorded. 

The  screw  a  is  again  loosened  and  the  rotation  continued  until 
the  signal  is  received  from  a  second  face,  this  is  centered  by  F  and 
a  and  recorded  as  before.  The  difference  between  the  two  read- 
ings is  the  supplement  angle  between  the  faces. 

At  least  three  measurements  of  any  angle  should  be  made  *  and 
averaged. 

THE  SYMMETRY  OF  CRYSTALS. 

There  is  in  almost  every  crystal  a  repetition  or  recurrence  of 
equal  angles  or  similarly  grouped  faces  and  to  this  the  name 
SYMMETRY  is  given. 

This  symmetry  may  be  no  more  than  that  each  face  has  an 
opposite  parallel  face.  Such  a  crystal  is  said  to  possess  a  center 
of  symmetry,  f 

Or  when  the  crystal  is  revolved  about  some  particular  line  each 
group  effaces  may  recur  2,  3,  4  or  6  times  during  the  revolution. 
Such  a  line  is  called  an  Axis  of  Symmetry.  \ 

Or  a  plane  may  so  divide  the  crystal  that  on  each  side  of  that 
plane  there  are  grouped  the  same  number  of  faces  at  the  same 

*  It  is  sometimes  recommended  to  use  different  portions  of  the  graduated  circle  for 
the  three  measurements.  For  instance,  for  the  second  measurement  when  the  signal 
from  the  second  face  is  centered  the  screw  b  is  loosened  and  the  crystal  alone  is  turned 
by  the  disk  e  until  the  signal  from  the  first  face  is  centered,  then  b  is  tightened  and  a 
loosened  and  the  crystal  and  circle  turned  together  as  before.  This  is  repeated  before 
a  third  measurement. 

f  A  model  is  symmetrical  to  ike  center  when  every  straight  line  through  the  center 
encounters  at  equal  distances  on  each  side  of  the  center  two  corresponding  points. 

J  A  model  is  symmetrical  to  an  axis  when  if  revolved  about  this  axis  the  model  re- 
occupies  the  same  position  in  spate,  two,  three,  four,  or  six  times  during  one  complete 
revolution.  That  is,  corresponding  groups  of  planes  exchange  positions  after  revolu- 
tions of  180°,  120°,  90°  or  60°. 


INTRODUCTORY. 


II 


FIG.  1 6. 


angles  to  it  and  to  each  other.     Such  a  plane  is  called  a  Plane  of 

Symmetry.  * 

Geometric  Symmetry  in  Models. 

True  geometric  symmetry  to  lines  and  planes  is  rarely  shown  by 
crystals,  all  that  is  found  is  symmetry  of  direction  rather  than  sym- 
metry of  position  and  size  of  the  bounding  faces. 

It  is  convenient,  however,  in  elementary  work,  to  make  use  of 
models  and  drawings  of  crystals  in  which  all  faces  symmetrical  in 
direction  are  made  equal  in  size  and  at  equal  distances  from  the 
center.  Such  a  shape  may  be  said  to  be  derived  from  the  natural 
crystal  by  moving  each  face  parallel  to  itself  until  all  correspond- 
ing faces  are  at  an  equal  distance  from  the  center.  Thus  in  Fig. 
8  the  little  inner  octahedron  is  the  ideal  shape  of  the  outer  actual 
crystal,  and  Fig.  2  is  the  ideal  shape  of  Fig.  5. 

Obtaining  the  Idea  of  Symmetry  from  Models. 

In  such  models  and  in  a  few  crystals  which  approximate  them 
in  shape  the  planes  and  axes  of  symmetry 
may  be  determined  by  viewing  the  crystal  in 
different  positions  and  noting  the  shape  and 
repetition  of  groups  of  faces. 

If,  as  in  Fig.  16,  a  plane  so  divides  the 
model  that  a  line  from  an  angle  b  perpendic- 
ular to  the  plane  passes  through  a  correspond- 
ing angle  a,  or  a  perpendicular  from  c,  the 
center  of  an  edge,  passes  through  d,  the 
center  of  a  similar  edge. 

Or  if  in  a  crystal  there  is  an  approximation 
to  this  so  that  a  'plane  appears  to  divide  it 
into  halves  symmetrical  to  each  other  as  to  the  number  and  direc- 
tion of  their  bounding  faces,  even  if  there  is  not  strict  geometric 
symmetry,  then  a  probable  plane  of  symmetry  has  been  found. 

So  also  if  a  model  can  be  revolved  about  a  line,  and  twice  or 
oftener  in  a  revolution  occupy  the  same  position  in  space,  or  if  in  a 
crystal  all  the  planes  seen  in  one  position  are  replaced  at  other 
positions  by  just  as  many  planes  which  are  grouped  as  in  the  first 
set,  then  a  probable  axis  of  symmetry  has  been  determined. 

*  A  model  is  symmetrical  to  a  plane  when  the  plane  so  divides  it  that  either  half  is 
the  mirrored  reflection  of  the  other,  and  every  line  perpendicular  to  the  plane  connects 
corresponding  parts  and  is  bisected  by  the  plane  of  symmetry. 


12 


CR  YSTALL  OGRAPHl '. 
FIG.   17.  FIG.   18. 


For  example,  the  crystal  of  gypsum,  Fig.  1 7,  is  symmetrical  to  the  axis  BB  ;  for,  <is 
shown  in  Fig.  18  both  when  the  point  a  has  moved  to  b  or  again  to  a  the  crystal  occu- 
pies the  original  position  in  space.  Moreover  for  any  intermediate  position  of  a  such  as 
c  the  space  occupied  is  distinctly  not  the  same.  That  is,  BB  is  an  axis  of  two-fold  or 
binary  symmetry. 


FIG.  20. 


FIG.  21. 


FIG.  22. 


The  line  CC'm  the  zircon  crystal,  Fig.  19,  is  an  axis  of  four-fold  or  tetragonal  sym- 
metry, for,  as  shown  in  the  horizontal  projection,  Fig.  20,  the  crystal  occupies  the  same 
position  in  space  when  any  point  a  has  moved  to  b,  c,  d  or  again  to  a,  and  does  not  for 
any  other  position. 

Finally  the  line  CC  in  the  apatite  crystal,  Fig.  21,  is  an  axis  of  six-fold  or  hexagonal 
symmetry,  because,  as  shown  in  horizontal  projection,  Fig.  22,  the  crystal  occupies  the 
same  position  in  space  when  any  point  a  has  moved  to  b,  c,  d,  e,  f  or  again  to  a. 

DETERMINATION  OF  CRYSTAL  SYMMETRY  BY  MEASURE- 
MENT  AND   PROJECTION. 

With  most  crystals  inspection  alone,  except  as  the  result  of 
long  practice,  will  not  reveal  the  symmetry  of  direction  which  they 
possess. 


L\TR  OD  UCTOR  Y.  1 3 

Some  simple  method  is  needed  by  which  this  symmetry  may  be 
found  from  the  angles  between  the  faces  and  the  most  satisfactory 
is  to  substitute  for  the  solid  form  a  projection  upon  a  plane. 

The  Method  of  Stereographic  Projection. 

The  crystal  is  assumed  to  be  surrounded  by  a  sphere,  the  centers 
of  the  sphere  and  the  crystal  coinciding,  and  radii  to  be  drawn 
from  the  center  perpendicular  to  each  face  of  the  crystal.  The 
point  where  any  such  radius  cuts  the  surface  of  the  sphere  is 
called  the  pole  of  the  corresponding  face. 

From  each  face  pole  such  as  P,  Fig.  23,  a  line  is  supposed  to  be 


Perspective  of  a  Stereographic  Projection. 

drawn  to  the  south  pole  S,  and  the  point  P'  where  this  line 
pierces  the  equatorial  plane  is  the  Stereographic  projection  of  the 
face  pole  P. 

If  all  the  face  poles  are  projected  in  this  way  there  results  a 
circle  dotted  with  points  from  the  positions  of  which  the  symmetry 
and  the  angles  can  be  determined. 

Thus  in  Fig.  23  the  radii  perpendicular  to  the  vertical  faces  of 
the  quartz  crystal  lie  in  the  equatorial  plane  and  any  face  pole  as 


1 4  CR  YSTALL  O  GRAPH  Y. 

L  coincides  with  its  stereographic  projection,  but  the  radii  perpen- 
dicular to  an  oblique  face  lie  in  some  meridian  plane  and  any  face 
pole  as  P  is  projected  at  the  intersection  P'  of  PS  with  the  equa- 
torial plane. 

Making  a  Stereographic  Projection. 

Preliminary.  Select  the  plane  of  projection,  usually  perpen- 
dicular to  a  zone  of  prominent  or  numerous  faces. 

Draw  a  circle  of  any  convenient  diameter,  say  that  of  Fig.  26, 
and  let  the  point  B,  Fig.  24,  be  taken  as  the  pole  of  a  chosen  verti- 
cal face. 

Projecting  the  Vertical  Faces.  Measure  the  supplement  angles 
between  this  face  and  the  other  vertical  faces  and  lay  off  these  upon 
the  circumference,  thus  determining  the  poles  L,  M,  B,  etc. 

FIG.  24. 


The  Angles  Needed  for  Projection  of  Oblique  Faces.  The  two- 
circle  goniometer  yields  at  once  for  any  face  two  angles  <f  and  ft 
for  instance  for  P,  Fig.  23,  <p  =  BL  and  p  =  CP.  If  a  two-circle 
goniometer  is  not  available  the  same  angles  may  often  be  obtained. 

(a)  If  /'lies  in  a  vertical  zone  with  a  vertical  face  L  then  <j>  is  the  same  for  both  and 
the  supplement  angle  LP  is  90°  —  p. 

(6)  If  P  makes  equal  angles  with  two  vertical  faces  (say  M  and  £}  then  <p  of  P  is 
midway  between  £>  for  M  and  B  and  the  supplement  angle  between  P  and  the  edge  of 
intersection  of  the  two  vertical  faces  is  90°  —  p. 

(c)  If  the  face  lies  in  two  known  zones  (that  is  if  observation  shows  the  face  to  make 
parallel  intersections  with  two  other  faces  and  a  second  set  of  parallel  intersections  with 
two  other  faces),  the  two  zone  circles  may  be  drawn  and  their  intersection  will  be  the 
desired  projection. 

Every  zone  in  stereographic  projection  is  a  circle  and  when  even  two  poles  of  a  zone 
are  known  a  circle  may  be  drawn  through  them  as  follows  : 


INTRODUCTORY. 


In  Fig.  25  given  /"and  Q  to  find  CPCr 

Draw  a  diameter  through  P.     The  face  /\  opposite  P,  will  be  on  it. 

Draw  OA  perpendicular  to  this  diameter,  draw  PA,  and  from  A,  a  line  perpen- 
dicular to  PA.      The  intersection  of  this  per- 

pendicular with  the  diameter  through  P,  will  FIG.   25. 

be  />j,  the  projection  of  the  pole  of  a  face 
opposite  P,  that  is  180°  from  /",  in  the  same 
zone. 

The  circle  through  the  three  points,  P,  Q 
and  Pv  will  be  the  desired  circle. 


Finding  the  Projection  of  the  Ob- 
lique Face.  The  desired  point  lies 
on  the  diameter  determined  by  <f 
and  at  a  distance  from  the  center 
equal  tang  1  p. 

This  distance  may  be  found  graphically  by  laying  off  the  arc 
ab  =  p,  Fig.  24,  drawing  be  then  is  OR  the  desired  distance  (the 
diameters  ac  and  BB  being  perpendicular  to  each  other). 

Or  the  distance  may  be  laid  off  from  the  center  by  a  protractor, 
Fig.  26,  devised  by  Prof.  Penfield,  in  which  the  values  of  the  stereo- 


FIG.  26. 


PROTRACTOR  No  I,  FOR  PLOTTING  STEREOORAPHIC  PROJECTIONS. 

The  graduation  on  the  base  line  gives  the  stereographically  projected  degrees. 

From  *  to  0  pquals  the  chord  of  90°. 


graphically  projected  degrees  have  been  prepared  for  a  circle  of 
convenient  size.  Knowing  p  and  the  diameter  on  which  the 
pole  is  projected,  the  o°  of  the  base  line  is  placed  at  the  center 
of  the  circle  and  the  distance  conesponding  to  p  (CP)  is  marked 
at  once. 


1 6  CR  YSTALL  OGRAPHY. 

Judging  Symmetry  from  a  Projection. 

1.  The  center  of  projection  is  a  center  of  3,  4  or  6  fold  symmetry 
and  the  projection  may  be  symmetrical  to  certain  diameters. 

Center.  Diameters.  System.  Class  of 

6  f.                      6  HEXAGONAL  DIHEXAGONAL  PYRAMID. 

4  f.       4  (2  are  4  f.  axes)  ISOMETRIC  HEXOCTAHEDRON. 

"        "  (none  are  4  f.  axes)  TETRAGONAL  DITETRAGONAL  PYRAMID. 

3  f-        3  (3  ^  ax's  m  plane  ISOMETRIC  HEXOCTAHEDRON* 

through  each)  OR  HEXTETRAHEDRON. 

"         "  (no  3  f.  axes)  HEXAGONAL  SCALENOHEDRON* 

OR  HEMIMORPHIC. 

"         none  ISOMETRIC  DIPLOID. 

2.  There  can  be  found  no  axis  of  3,  4  or  6  fold  symmetry  : 

Center.  Diameters.  System.  Class  of 

2  f.  2  ORTHORHOMBIC  PYRAMID. 

"  none  MONOCLINIC  PRISM. 

not  a  center  MONOCLINIC  PRISM. 

of  symmetry 

"  none  TRICLINIC  PINACOID. 

Thus  in  Fig.  24  there  is  a  center  of  6-fold  symmetry  and  six 
diameters  of  symmetry,  hence  geometrically  the  crystal  is  referred 
to  the  class  of  the  dihexagonal  pyramid. 

This  is  tentative,  other  crystals  of  the  same  substance  may  re- 
veal faces  which  lower  the  symmetry  and  indeed  the  true  symmetry 
of  a  crystal  is  known  only  when  all  the  characters  have  been  con- 
sidered. Structurally  equivalent  directions  not  only  imply  similar 
groupings  of  bounding  faces  but  physical  identity  in  all  respects 
and  two  directions  are  not  structurally  equivalent  if  in  these  direc- 
tions there  is  revealed  any  essential  difference  in  behavior  with 
polarized  light  or  etching  or  pyro-electricity  or  with  any  other 
test,  the  results  of  which  depend  upon  the  manner  the  crystal 
molecules  are  built  together. 
The  Law  of  Symmetry. 

The  Law  of  Symmetry  may  be  stated  as  follows  : 

All  crystals  of  any  one  substance  are  of  the  same  grade  of 
symmetry. 

That  is,  in  each  crystal  of  the  substance,  wherever  found  or  under 
whatever  conditions  formed,  there  will  be  the  same  number  and 

*  In  the  classes  of  the  hexoctahedron  and  scalenohedron  each  face  has  an  opposite 
parallel  face  but  in  the  classes  of  the  hextetrahedron  and  hemimorphic  hexagonal  this 
is  not  so.  The  test  can  usually  be  made  accurately  enough  by  placing  any  face  in  con- 
tact with  a  horizontal  surface. 


INTR  OD  UCTOR  Y.  I  / 

arrangement    of   planes    of    symmetry   and    axes    of    symmetry. 
The  crystals  will  not  all  be  alike  in  shape  even  when  the  varia- 


FIG. 27. 


FIG.  29. 


FIG.  30. 


tions  due  to  size  and  to  unequal  development  of  faces  have  been 
eliminated. 

Thus,  for  instance,  Figs.  27  to  29,  representing  different  crystals 
of  the  mineral  barite  (BaSO4),  are  all  symmetrical  to  three  planes 
placed  as  in  Fig.  30  and  to  three  axes 
formed  by  their  intersections. 

Calcite,  CaCO3,  occurs  in  over  200 
distinct  forms  with  different  angles  and 
in  innumerable  different  combinations 
of  these  forms  in  all  of  which  the 
symmetry  is  the  same. 

t^ 

Crystallographic  Axes. 

The  position  of  any  plane  in  space  is  known  if  three  of  its  points, 
not  in  the  same  straight  line,  are  known.  If  three  (in  one  system 
four)  straight  lines  passing  through  the 
center  of  the  crystal  are  chosen  as  crystal- 
lographic  axes-fch-ari  any  face  CDE,  Fig.  3 1 , 
may  be  defined  in  position  by  the  distances 
OA,  OB,  OC,  along  these  axes  from  the 
center  to  their  intersections  with  the  plane 
ABC  of  which  the  face  CDE  is  a  part. 

If  stated   as    relative   distances,    for   in- 
stance 

OA-.OB:  OC=o.7  :  i  10.82, 

these  intercepts  become  independent  of  the 
absolute  position  of  the  face  CDE  and  repre- 
sent any  face  parallel  to  it ;  that  is  any  face  at  certain  angles  to 
the  axes  however  large  the  crystal  may  be. 

Moreover  if  the  direction  from  0  is  disregarded  they  represent 
other  faces  CIK,  etc. 


FIG.  31. 


i8 


CR  YSTALL  OCR  A  PHY. 


Forms. 

Faces  such  as  CDE,  CIK,  CDL,  etc.,  which  cut  the  crystal  axes  at  the  same  rela- 
tive distances  from  the  center  are  said  to  belong  to  the  same  "  form."  The  "form" 
will  consist  of  just  enough  such  faces  to  satisfy  the  symmetry  of  the  crystal.  If  only  two 
faces  are  required  then  these  two  constitute  a  "  form." 

The  Possible  "  Forms  "  on  Crystals  of  One  Substance. 

Experience  proves  that  well  developed  faces  *  upon  crystals  of 
the  same  substance  occur  at  particular  angles  dependent  upon  the 
structure.  For  instance,  if  the  ultimate  particles  in  a  plane  through 
two  of  the  chosen  axes  BB  and  CC  were  as  in  Fig.  32,  then  the 
most  probable  faces  would  be  those  passing  through  the  greatest 
number  of  points,  that  is,  the  directions  TT,  TS  and  BC  (or  BC). 

FIG.  32. 
c 


The  next  in  probability  would  be  BE  (or  BE)  and  still  less  prob- 
able BD  (or  BD)  and  BH  (or  BH). 

These  directions  would  be  absolutely  determined  if  the  relative 
distances  apart  of  consecutive  points  on  CC  and  BB  were  known. 
In  the  figure  these  are  3:5,  hence  the  angles  with  BB  are : 

Direction.  Natural  talgent. 

TT 
TS 
BC 

BE 

BD  3X3:4X5=0.45 

BH  1X3:4X5=0.15 

The  Fundamental  Law  of  Rational  Intercepts. 

In  the  example  given  if  the  intercepts  on  BB  and  CC  are  re- 

*  There  exist  minute  so-called  "  vicinal  "  planes  which  are  not  solely  the  results  of 
cohesive  attraction,  but  also  of  disturbing  causes  such  as  concentration  currents.  See 
Gaubert,  Bull.  Soc.  Franc.,  Vol.  27,  pp.  6-48. 


I  -r-  00  =O 

00   ;    I  =00 

4X3:4X5=0.6 


Angle. 

1 80° 
90° 

30°  58' 
1 6°  42' 
26°  45 ' 
8°  32' 


INTR  OD  UCTOR  Y.  1 9 

duced  so  that  for  each  direction  one  term,  for  instance  the  inter- 
cept on  CC,  is  unity  the  other  terms  bear  a  very  simple  relation 
to  eacli  other.  Any  one  is  a  simple  multiple  or  factor  of  any 
other/  /For  BC,  BE,  BD,  BH  the  intercepts  on  BB  are  relatively 
6o:£fc:45  :  15  or  4:  2  :  3  :  i. 

Such  a  simple  relation  is  found  always  to  exist  for  faces  which 
are  true  crystal  faces  and  it  has  been  expressed  as  follows : 

hi  all  crystals  of  the  same  cJiemical  substance,  if  the  intercepts  of 
ANY  face  upon  the  crystallographic  axes  are  divided,  term  by  term,  by 
the  corresponding  intercepts  of  ANY  OTHER  face,  the  quotients  will 
always  be  simple  rational  numbers  or  infinity. 

For  instance  in  a  certain  substance  the  three  axes  are  cut  by  two 
faces  in  distances  which  after  reduction  are 

0.813  :  i  :  1.903 
1.626:  i  :  5.709. 

Dividing  the  second  by  the  first,  term  by  term,  there  result  2,  i,  3. 
A  face  with  intercepts  relatively  1.734  :  i  :  6.275  could  not  occur 
upon  this  crystal  or  upon  any  other  crystal  of  this  substance  because 

--•—  =  2.1328  +  and  -'-^  =  3.2973  -f  that  is,  the  quotients 
0.813  I-9°3 

obtained  by  dividing  corresponding  terms  are  not  simple  numbers 
or  infinity. 

The  Weiss  Symbols. 

In  order  to  compare  the  intercepts  of  the  different  faces  of  a 
crystal  Prof.  Weiss  designated  the  values  of 
the  intercepts  AO,   OB,  and  OC  of  some  F^G'  33> 

chosen  face  BCMN,  Fig.  33,£>y  a,  b  and  c  |\ 

respectively  and  the  face  by  the  symbol  ;j    \ 


Then   according  to  the  law  of  rational 
intercepts,   any  other  possible  face  on  that 
crystal  as  MND  would   have  such   inter- 
cepts that  divided  term  by  term  the  quo- 
tients would  be  simple  rational  numbers  or 
infinity.      In  this  case  it  is  at  once  seen  by      /.*?.:'-'•-'-'•'' 
drawing  FHL  parallel  to  BCMN,  since  the    - 
symbol  of  FHL  is  also  a\b\c,  that  the  symbol  of  MND  is  Jtf  :  b  :  2c, 
which  may  be  written  &^§b  :  6&r- 

L  •.  Vfc  \fe«- 


20  CR  YSTALLOGRAPHY. 

The  Miller  Indices. 

The  symbols  of  Weiss  *  have  been  very  generally  superseded 
by  condensed  expressions  which  are  more  convenient  for  pur- 
poses of  calculation.  Chief  among  these  are  the  so-called  Miller 
Indices. 

In  these  the  chosen  or  unit  face  is  assumed  to  be  moved  parallel 
to  itself  until  it  is  outside  of  all  the  other  faces,  then  the  intercepts 
of  these  faces  are  all  fractional  parts  of  the  unit  intercepts. 

If  then  these  fractions,  written  in  the  order  of  the  axes  OA, 
OB,  OC,  are  reduced  by  dividing  each  by  the  least  common  multiple 

of  the  numerators  there  result  three  fractions  T,     ...     The  de- 

k?  k*  I 

nominators  of  these  fractions  are  the  Miller  indices,  that  is  !ikl  is 
the  general  Miller  symbol  for  any  face. 

It  is  no  harder  to  realize  the  position  of  a  face  from  an  expres- 
sion i  2  3  than  from  the  equivalent  a\^b\  \c.  Each  means  that 
the  intercepts  in  comparison  to  the  intercepts  of  the  chosen  unit  face 
and  in  the  same  order  are  the  same  length,  half  as  long  and  one 
third  as  long. 
Choosing  Crystallographic  Axes. 

It  is  always  possible  and  indeed  essential  to  choose  as  crystallo- 
graphic  axes  those  lines  which  are  closely  related  to  the  symmetry 
of  the  crystal.  The  choice  should  be  made  in  the  following  order  : 

First,  axes  of  symmetry. 

Second,  lines  perpendicular  to  planes  of  symmetry. 

Third,  lines  parallel  or  equally  inclined  to  several  faces  of  the 
crystal. 

In  some  crystals  there  may  be  more  lines  of  equal  prominence 
than  are  needed.  Preference  should  then  be  given  : 

(a)  To  directions  at  right  angles  to  each  other. 

(ff)  To  interchangeable  directions,  that  is  to  directions  such  that 
the  grouping  of  the  faces  about  one  is  the  same  as  the  grouping 
of  the  faces  about  the  other. 
The  Six  Systems. 

The  six  systems  already  mentioned  under  symmetry  may  then 

*  Weiss  coefficients  and  Miller  indices  are  essentially  reciprocals  of  each  other.  For 
instance,  a  plane  with  indices  (432)  means  \a  :  \b  :  \c,  and  making  a,  for  instance, 
unity,  we  have  a  :  \b  :  2c  as  the  Weiss  symbol.  Conversely,  a  plane  with  a  symbol 
$a :  b  :  ^c  is  first  reduced  to  a  :  \b  :  \c  ;  then,  taking  reciprocals,  (i  5  3)  is  the  Miller 
symbol. 


INTR  OD  UCTOR  Y.  2 1 

be  defined  each  as  including  all  crystals  which  are,  by  the  given 
rules,  referred  to  a  particular  set  of  axes  : 

THE  TRICLINIC  SYSTEM. — Three  non-interchangeable  axes  at 
oblique  angles  to  each  other. 

THE  MONOCLINIC  SYSTEM. — Three  non-interchangeable  axes  two 
of  which  are  oblique  to  each  other,  the  third  is  at  right  angles  to 
the  other  two. 

THE  ORTHORHOMBIC  SYSTEM. — Three  axes  at  right  angles  but 
not  interchangeable. 

THE  TETRAGONAL  SYSTEM. — Three  axes  at  right  angles,  of  which 
two  are  interchangeable. 

THE  HEXAGONAL  SYSTEM. — Four  axes,  three  of  which  lie  in  one 
plane  at  sixty  degrees  to  each  other  and  are  interchangeable,  the 
fourth  is  at  right  angles  to  the  other  three. 

THE  ISOMETRIC  SYSTEM. — Three  interchangeable  axes  at  right 
angles  to  each  other. 
Determination  of  Type  Symbols  by  Inspection. 

After  the  axes  have  been  chosen,  as  described  and  placed  in  the 
conventional  positions  stated  under  each  system,  the  determination 
of  the  type  symbols  may  be  conducted  as  follows  in  models  and 
large  crystals : 

Place  a  straight  edge  or  pencil  in  contact  with  a  face  and  turn 
the  straight  edge  always  as  a  line  in  the  face  until  its  relation  to 
each  axis  has  been  noted.  The  absolute  values  of  the  axial  inter- 
cepts are  not  needed  to  determine  the  type  of  form ;  all  that  is 
essential  is  to  note  parallelism  and  equality. 

If  it  is  not  evident  that  all  the  faces  of  the  figure  hold  the  same 
relation  to  the  axes,  any  supposedly  different  face  is  tried  in  pre- 
cisely the  same  way  with  the  straight  edge  and  with  respect  to  the 
same  axes.  If,  when  the  face  is  parallel  to  one  of  the  axes,  the  cor- 
responding index  is  designated  o  in  Miller  or  by  oo  in  Weiss,  we 
will  have  seven  possible  type  symbols : 

MILLER.  WEISS. 

Unit  (in)  Unit  a\b\c 

1.  The  face  cuts  all  axes  hkl  na:b\  me 

2.  "      "    is  parallel      AA  &kl  coa:b:mc 


BB~  ho!  a :  co  b  :  me 

CC  hkQ  na  '.  b  :  coc 

AA  and  BB  ooi  oo«  :  oo3  :  c 

AA    "    CC  oio  CD*  :  /;  :  <oc 

BB     "    CC  100  a  :  co/;  :  oo<r 


22 


CR  ]  STALLOGRAPHY. 


Determination  of  Type  Symbols  in  a  Stereographic  Projection. 

If  measurements  have  been  made  the  resulting  Stereographic 
projection  yields  the  same  seven  type  symbols,  5,  6  and  7,  being 
each  limited  to  one  form,  but  the  other  types  including  more  than 
one  form  according  to  the  values  of  the  intercepts.  The  position 
of  the  forms  for  one  particular  ratio  hkl  in  a  system  with  the  crys- 
tallographic  axes  at  right  angles,  is  shown  in  Fig.  34. 

FIG.  34. 


hO 


.<. 


XBt 

«%« 


"I 


*       u    ^ 


,V 


X 

K  N 

V%A&* 


N 


A>  $ 


....4-     (>N     ^) 

S^5;» 


\ 


H     * 
^   "^ 


^  N 


ri 


i 


v"^^  ^"<  V  '  v    «  ^^r^^  ^ 

^UV|    |]S 

UKkk 


Jia^- 


^i^^ 
^«i 


\      O 


-i  ^~ 
t  .£;<. 


\^^^S  ^  x^-\  ^  "S^SJ^ 

^^*^VH^ 


L.* 


>    N  xvl  v  •<;  <  -^ 
\  ^  Ji^*^ 

^       >       0    0    V      N     X     ^ 


swim 


'•A 


,- 


-' 


x    ""*  "' 

r  ••  < 


Z       •' 


s  *  '      Tr  » 


,    x 
tf  <^r< 

\ 


CHAPTER   II. 


TRICLINIC    SYSTEM.* 

THE  Triclinic  System  includes  two  classes  in  both  of  which  the 
crystallographic  axes  are  three  lines  oblique  to  each  other  and  not 
interchangeable. 

PINACOIDAL    CLASS.     2. 

No.  31.   Holohedry,  Liebisch.     No.  31.   Normal  Class,  Dana. 

Choosing  Crystallographic  Axes. 

Usually  the  intersections  of  three  prominent  faces  are  chosen  as 
axes  and  one  is  conventionally  made  the  vertical  axis  c,  the  others 
the  macro  or  ~b  axis  and  the  brachy  or  ft  axis. 

The  Seven  Type  Forms. 

Each  form  consists  of  two  parallel  faces  as  follows : 

i .  TETRAPYRAM ID.  —  nd  \  b  :  me ;   { hkl } . 

Two  parallel  faces  which  intersect  all  axes,  Fig.  35.  For  any 
set  of  intercepts  four  independent  forms  result  which  if  combined 
make  a  complete  triclinic  pyramid  as  shown  in  Fig.  36.  Fig.  4.3 


FIG.  35. 


FIG.  36. 


FIG.  37. 


shows  two  tetra -pyramids  p'  =  a\b  \c=  in   and  'p  =  a  :  b'  \c 
1 1 1  of  the  mineral  axinite. 


*  Also  known  as  Tetarto  prismatic,  Ein-und-eingliedrige,  Triclinohedral,  Clinorhom- 
boidal,  Anorthic,  Doubly  oblique  and  Asymmetric. 

23 


CR  YSTALLOGRAPHY. 


2.  HEMI  BRACHY  DOME.  —  oo  d  :  b  :  me  •   {okl}. 

Two  faces  each  parallel  to  the  brachy  axis.     The  face  e  and  its 
opposite,  Fig.  37,  modifying  the  three  pinacoids. 

3.  HEMI  MACRO  DOME. — a:<x>bzmc;   {hoi}. 

Two  faces  each  parallel  to  the  macro  axis.     The  face  d  and  its 
opposite,  Fig.  38,  modifying  the  pinacoids. 

4.  HEMI  PRISM.  —  nd:b:coc\   {hko}. 

Two  faces  each  parallel  to  the  vertical  axis.     The  face  ;//  and 
its  opposite,  Fig.  39,  modifying  the  pinacoids. 

5.  BASAL  PINACOID. —  coft-cob-.c;   {ooi}. 

Two  faces  each  parallel  to  both  the  macro  and  brachy  axes.     The 
faces  c  in  Figs.  38  to  40. 


FIG.  38. 


FIG.  39. 


FIG.  40. 


6.  BRACHY  PINACOID. — co£:£:coc;   {oio}. 

Two  faces,  each  parallel  to  the  brachy  and  vertical   axes.      The 
faces  b  of  Figs.  38  to  40. 

7.  MACRO  PINACOID. — fl  :cob  :  coc;   {ioo}. 

Two  faces  each  parallel  to  the  macro  and  vertical   axes.     The 
faces  a  of  Figs.  38  to  40. 
Combinations  in  the  Triclinic  System. 

Fig.  41  shows  a  crystal  of  chalcanthite  with  brachy  pinacoid  b, 


FIG.  41. 


FIG.  42. 


TRI CLINIC  SYSTEM.  2$ 

macro  pinacoid  a,  right  hemi  prism  m,  left  hemi  prism  M  and  lower 
left  tetra  pyramid  'p.  Fig.  42  shows  a  crystal  of  cyanite  with  the 
three  pinacoids  a,  b  and  <r,  the  right  m,  and  left  M  hemi  unit  prisms 
and  a  right  hemi  brachy  prism  /  =  (2,0, :  b  :  oo  c) ;  { 1 20} . 

Fig.  43  shows  a  crystal  of  axinite  with  both  hemi  prisms  m  and 
M,  macro  pinacoid  a,  upper  right  and  upper  left  unit  pyramids  /' 
and  ' p  and  a  macro  dome  e  =  (fi  :  oo  ^  :  2<r.) ;  { 201 } . 


Other  Classes  in  Triclinic  System. 

One  other  class  known  as  the  unsymmetrical  class  exists  and  in 
this  each  form  is  a  single  face.  No  examples  among  minerals  are 
known  but  among  salts  there  is  calcium  thiosulfate,  CaS2O3  •  6H2O. 


CHAPTER  III. 


MONOCLINIC   SYSTEM.* 

THE  monoclinic  system  includes  three  classes  of  symmetry,  in 
all  of  which  the  crystallographic  axes  may  be  chosen  so  that  two 
are  oblique  to  each  other  and  the  third  normal  to  the  other  two. 
The  axes  are  not  interchangeable. 

PRISMATIC   CLASS.     5. 

No.  28.   Holohedry,  Liebisch.     No.  28.   Normal  Group,  Dana. 


FIG.  44. 


All  the  common  monoclinic  minerals  occur 
in  crystals  symmetrical  to  one  plane  and  to 
one  axis  at  90°  to  the  plane,  Fig.  44. 
Choosing  Crystallographic  Axes. 

The  axis  of  symmetry  is  always  chosen  as 
the  axis  b  and  placed  horizontally  from  right 
to  left. 

Two  other  axes,  oblique  to  each  other,  are 
chosen  f  in   the  plane  of  symmetry  one  of 
which  is  placed  vertically  and  denoted  by  c  the 
other  a  "the  clino"  dips  downward  from  back 
to  front.     The  acute  angle  between  the  verti- 
cal and  clino  axis  is  called  ft. 
Tabulation  of  the  Seven  Type  Forms. 


NAME. 

FACES. 

WEISS. 

MILLER. 

Each  face  intersects  all  axes  : 

i.  HEMI  PYRAMID, 

4 

nd  '.  b  '.  me 

{hkl} 

Each  face  parallel  to  one  axis  : 

2.  CLINO  DOME, 

4 

cod  '.  b~\  me 

{<>*!} 

3.  HEMI  ORTHO  DOME, 

2 

a:  oo?:  me 

{hoi} 

4.  PRISM, 

4 

nd  :  7  :  coc 

{hko} 

Each  face  parallel  to  two  axes  : 

5.  BASAL  PINACOID, 

2 

cod  :  co3  :  c 

{001} 

6.  CLINO  PINACOID, 

2 

cod  '.  b  ;  toe 

{010} 

7.  ORTHO  PINACOID, 

2 

A  :  oo^  :  coc 

[too] 

*  Also  called  Hemiprismatic,  Zwei-und-eingliedridge,  Monoclinohedral,  Clinorhom- 
bic,  Monosymmetric. 

f  For  instance  the  intersections  of  the  pinacoids  would  determine  both  directions,  or 
the  edges  of  any  prism  and  any  clino  dome  would  determine  both  directions. 

26 


MONO  CLINIC  SYSTEM. 


Description  of  the  Type  Forms. 

I.   HEMI  PYRAMID. — na  \b\mc\  {hkl}. 

Four  faces  each  intersecting  all  the  axes  in  distances  not  simple 
multiples  of  each  other.  Fig.  45  shows  a  negative  form  cut  ofT 
by  a  positive  ortho  dome  o. 

For  any  set  of  intercepts  two  independent  forms  result  which 
combined  form  a  complete  pyramid.  For  instance  the  combination 
of/,  Fig.  45,  with  the  corresponding  positive  form/  gives  Fig.  46. 


FIG.  45. 


FIG.  46. 


2.  CLINO  DOME. — coa:&:mc; 

Four  faces,  each  parallel  to  the  clino  axis  and  cutting  the  verti- 
cal and  ortho  axes  in  distances  not  simply  proportionate.  The 
faces  d  of  Fig.  47  combined  with  two  pinacoids. 

3.  HEMI  ORTHO  DOME. — a  :<x>b;c;   {hoi}. 

Two  opposite  faces,  each  parallel  to  the  ortho  axis  and  cutting 
the  clino  and  vertical  axes  in  distances  not  simply  proportionate. 
The  faces  o  in  Figs.  45  and  48  are  the  positive  hemi  ortho  dome. 
Another  independent  form  exists  with  the  same  intercepts. 

FIG.  47.  FIG.  48.  FIG.  49. 


4.   PRISM.  —  na  :  "b  :  oo  c  ;   [hko] . 

Four  faces,  each  parallel  to  the  vertical  axis,  and  cutting  the 


28 


CR  YSTALLOGRAPHY. 


basal  axes  in  distances  not  simply  proportionate.     The  faces  m  in 
Fig.  48  and  subsequent  figures. 

5.  BASAL  PIN ACOID.  —  coa:co7>:c;   {ooi}. 

Two  faces,  each  parallel  to  both  basal  axes.  The  faces  c  of 
Fig.  49  and  subsequent  figures. 

6.  CLINO  PINACOID. — coa:7>:cDc;   {oio}. 

Two  faces,  each  parallel  to  the  clino  and  vertical  axes.  The 
faces  b  of  Fig.  49  and  subsequent  figures. 

7.  ORTHO  PINACOID. — a:co^:coc;   {100}. 

Two  faces,  each  parallel  to  the  ortho  and  vertical  axes.  The 
faces  a  of  Fig.  49  and  subsequent  figures. 

Combinations  in  the  Prismatic  Class. 

Pyroxene.  —  Axes  a  :  ~b  :  c  =  1.092  :  i  :  0.589;  /9  =  74°  10'  9". 

Fig.  50  shows  the  three  pinacoids,  a,  b  and  c,  the  unit  prism  m, 
the  negative  unit  hemi-pyramid  /  and  the  positive  hemi-pyramid  v 
=  (a  :  1)  :  2.0] ;  {221}.  Fig.  52  is  the  same  without  v  and  Fig.  51 
omits  also  the  basal  pinacoid  c.  Fig.  5  3  shows  the  unit  prism  m,  the 


FIG.  50. 


FIG.  51. 


FIG.  52. 


FIG.  53. 


y 


basal  pinacoid  c,  two  positive  hemi-pyramids  v  and 
{331};  and  a  clino  dome  s  =  (co  a  :  b  :  2c];   {021}. 
AMPHIBOLE.  —  Axes  a  :  b  :  c  =  o.  5  5  1  ;  i  :  o.  293  5^=73 

FIG.  54.  FIG.  55. 


58' 4' 


FIG.  56. 


MO  NO  CLINIC  SYSTEM. 


29 


Fig.  54  shows  the  unit  prism  ;;/,  the  basal  and  clino  pinacoids,  c 
and  b  and  the  positive  unit  hemi  pyramid  /.  Fig.  55  shows  the 
unit  prism,  clino  pinacoid  and  unit  clino  dome  d=  (co  a  :  ~b  :  <:). 
{oil}.  Fig.  56  shows  the  same  except  that  the  clino  pinacoid  b 
is  replaced  by  the  ortho  pinacoid  a. 

FIG.  57.  FIG.  58.  FIG.  59.  FIG.  60. 


ORTHOCLASE.  —  Axes  a\  b\  c  =  0.658  ;  1:0.551;;  ,3  =  63°  56' 
46". 

Fig.  57  shows  the  unit  prism  m,  clino  and  basal  pinacoids  b 
and  r,  and  positive  hemi  orthodome  y  =  (a  :  co£  :  2<r);  {201}.  In 
Fig.  58  y  is  replaced  by  o  =  (a  :  co  1)  :  c] ;  { 101 }  and  in  Fig.  60 
the  clino  pinacoid  is  omitted.  Fig.  59  includes  the  forms  of  57 
and  also  a  clino  prism  z=  (30  \~b\  cor) ;  {130}  and  the  unit 
pyramid  /. 


Other  Classes  in  the  Monoclinic  System. 
Two  other  classes  are  known : 

3.  CLASS  OF  THE  MONOCLINIC  SPHENOID.     With  one  axis  of 
2-fold  symmetry. 

No  examples  among  minerals  are  known.     Examples  in  salts 
are  tartaric  acid  and  cane-sugar,  C12H22OU.  <Q 

4.  CLASS    OF   THE    MONOCLINIC    DOME.     With    one   plane    of 
symmetry. 

Examples  :  The  rare  minerals  clinohedrite  and  scolecite. 


CHAPTER   IV. 


ORTHORHOMBIC    SYSTEM. 

THE  orthorhombic  *  system  includes  three  classes  of  symmetry, 
in  all  of  which  the  crystallographic  axes  may  be  chosen  at  right 
angles  to  each  other,  but  are  not  interchangeable. 

In  this  system  of  moderate  symmetry  certain  facts  common  to 
all  crystals  can  be  better  illustrated  and  understood  than  in  the 
other  systems.  Two  of  these  are  discussed  under  the  headings 
"  Series  "  and  "  Symbols  for  Individual  Faces." 

Series. 

All  forms  which  ever  appear  upon  crystals  of  the  same  sub- 
stance belong  to  one  series.  That  is,  their  faces  occur  at  such 
angles  that  if  one  of  the  faces  is  taken  as  the  unit  and  its  intercepts 
expressed  by  d  :  b  :  c  all  other  faces  may  be  simply  expressed  in 
terms  of  this  face.  For  instance  in  the  crystals  of  topaz,  Figs.  78 
to  80,  the  calculated  intercepts  for  certain  faces  and  their  symbols, 
when  /  is  taken  as  the  unit  face,  are  as  follows  : 


FACE. 

i 

<1 
m 
I 

f 

h 


CALCULATED  INTERCEPTS. 


0.528  : 
0.528 : 
0.528: 
0.528: 
1.156 : 


••0-477 
:o.3i8 
=  0.954 


SYMBOLS  IN  TERMS  OF  /. 
a   :  ~b   :  c          {III} 

a  :  ~ 


0-954 
.-00:9.318 


2a 

cod 


2  c 
oo  c 


{223} 
{221} 
{110} 
{120} 
{021} 
{203} 


Symbols  for  Individual  Faces. 

For  correct  projection  and  for  use  in  calculation  face  symbols 
are  needed  which  show  the  particular  angle  in  which  the  face 
occurs.  These  are  simply  obtained  by  considering  positive  and 
negative  directions  upon  the  crystal  as  in  the  figure.  Then  the 
different  faces  of  Fig.  6 1 ,  for  which  the  form  symbol  is  no.  :  b  :  me 
or  {&&/},  have  their  individual  symbols,  (hkl\  (hkl\  (hkl\  (//£/), 
the  minus  signs  indicating  the  negative  direction  and  the  paren- 

*  Also  called  Prismatic,  Rhombic,  Ein-und-einaxige,  Anisometric  and  Trimetric. 
3° 


ORTHORHOMBIC  SYSTEM. 

theses  (  )  typifying  a  face  as  opposed  to  {  }  for  a  form.  Or  in 
Weiss' s  Symbols  the  equivalents  may  be  obtained  either  by  use  of 
minus  signs  or  a  (')  prime  upon  the  negative  intercept  thus  the 
equivalent  for  (hkl)  would  na:b' :mc. 

PYRAMIDAL   CLASS.     8. 

No.  25.      Holohedry,  Liebisch.      No.  25.      Normal  Group,  Dana. 

Almost  all  orthorhombic  minerals  crystallize  in  forms  sym- 
metrical to  three  planes  at  right  angles  to  each  other,  as  in  Fig. 
62,  the  intersections  of  these  being  axes  of  two-fold  symmetry. 

FIG.  61.  FIG.  62. 


Choosing  Crystallographic  Axes. 

The  axes  of  symmetry  are  the  crystallographic  axes.  One,  c,  is 
placed  vertically.  Of  the  two  others  the  one  on  which  the  inter- 
cept of  the  chosen  imit  face  is  the  longer,  is  placed  from  left  to 
right,  and  called  the  macro  or  b  axis ;  the  other  axis,  placed  from 
front  to  back,  is  called  the  brack}'  or  d  axis. 

The  unit  face  chosen  will  if  possible  be  a  face  of  frequent  occurrence  which  inter- 
sects all  the  axes,  or  on  account  of  similarity  of  crystals  to  some  species  of  related  com- 
position, another  choice  may  be  made  or  the  values  a,  b  and  c  may  result  from  two  dif- 
ferent faces  or  from  cleavages. 

Tabulation  of  the  Seven  Type  Forms. 

NAME.  FACES.           WEISS.           MILLER. 
Each  face  intersects  all  axes  : 

1.  RHOMBIC  PYRAMID.  8            na:~b\mc            hkl} 
Each  face  parallel  to  one  axis  : 

2.  BRACHY  DOME.  4            coa-.b-.mc          {oM} 

3.  MACRO  DOME.  4            <? :  co3 :  me          {^o/} 

4.  RHOMBIC  PRISM.  4            nu:~b:mc           [hko] 


CR  YSTALLOGRAPHY. 


»       NAME.  FACES. 
Each  face  parallel  to  two  axes  : 

5.  BASAL  PINACOID.  2 

6.  BRACHY  PINACOID.  2 

7.  MACRO  PINACOID.  2 


WEISS. 


MILLER. 


-'oio1 


Description  of  the  Type  Forms. 

i.   RHOMBIC  PYRAMID. —  nd  :~b  :  me  ;   {hkl}. 

Eight  faces,  each  of  which  cuts  the  three  axes  in  the  same  relative 
distances,  which  are  never  simple  multiples  of  each  other.  In  the 
ideal  forms  the  faces  are  equal  scalene  triangles. 

A  pyramid  may  be  composed  either  of  faces  with  the  unit  inter- 
cepts, or  the  faces  may  be  at  other  angles,  with  any  one  or  two 
of  the  intercepts  simple  multiples  of  the  unit  intercepts. 

For  instance  if  in  the  series  of  figures  63  to  67  the  faces  p  con- 
stitute the  unit  pyramid  ft  :  b  :  c  ;  {in};  then  a  series  of  pyramids 
which  might  occur  with  this  would  have  different  symbols  and 
names.  The  pyramid  s,  shown  in  Fig.  63  enclosing  p  and  in  Fig. 


FIG.  63. 


FIG.  64. 


FIG.  65. 


FIG.  66. 


FIG.  67. 


64  combined  with  p  ;  would  be  called  a  brachy  pyramid,  its  symbol 
being  20.  :  ~b  :  \c\   (364). 


ORTHORHOMBIC  SYSTEM. 


33 


The  pyramid  w  shown  in  Fig.  65  enclosing  /  and  in  Fig.  66 
combined  with  p  would  be  called  a  macro  pyramid,  its  symbol  be- 
ing d  :  I? :  %c  ;  {322}  ;  and  the  pyramid  r  shown  in  Fig.  67  com- 
bined with  /  would  be  called  a  unit  series  pyramid,  its  symbol  be- 
ing a  :  1 :  2c  •  {221}. 

2.  BRACHY  DOME.  —  oo d  :  b  :  me  ;   {okl}. 

Four  faces,  each  parallel  to  the  brachy  axis  but  cutting  the 
macro  axis  and  vertical  axis  in  distances  not  simply  proportionate. 
The  faces  d  in  Fig.  68. 

3.  MACRO  DOME. — &\v>b\mc\   {hoi}. 

Four  faces,  each  parallel  to  the  macro  axis  but  cutting  the 
brachy  axis  and  the  vertical  axis  in  distances  not  simply  propor- 
tionate. The  faces  o  in  Fig.  69. 

FIG.  68.  FIG.  69. 


4.  RHOMBIC  PRISM. — n&\b\v>c\   {hko}. 

Four  faces,  each   parallel   to  the  vertical  axis  and  cutting  the 
basal  axes  in  distances  not  simply  proportionate. 

The  intercepts  on  the  basal  axes  may  be  in  the  unit  ratio  or 


FIG.  70. 


FIG.  71. 


one  of  the  intercepts  may  be  relatively  lengthened  just  as  in  the 
pyramids. 

The  faces  m  in  Fig.  68.     In  Fig.  70  if  /  is  the  unit  pyramid 
then,  relatively,  m  is  the  unit  prism  a  :  b  :  CDC  ;   {no};  and  /  is  a 
brachy  prism  2d  :  b  :  oo  c ;  { 1 20} . 
3 


34 


CR  YSTALL  OGRAPHY. 


5.  BASAL  PINACOID. — cod:cob:c;   {ooi}. 

Two  faces,  each  parallel  to  the  basal  axes.  The  faces  c  in  Figs. 
71-80. 

6.  BRACHY  PINACOID.  —  co#:^:oo<r;   {oio}. 

Two  faces,  each  parallel  to  the  brachy  and  vertical  axes.  The 
faces  b  in  Figs.  69  and  71. 

7.  MACRO  PINACOID. — d  :<x>b  :coe;   {100}. 

Two  faces,  each  parallel  to  the  macro  and  vertical  axes.     The 
faces  a  in  Fig.  7 1 . 
Combinations  in  the  Pyramidal  Class. 

Barite. — Axes  d  :  b  :  c  =  0.8 1 5  :  i :  i .3 1 3. 

The  prevailing  faces  are  the  unit  prism  m,  the  basal  pinacoid  c, 
the  macro  dome  n  =  (&  :  oo  b :  |r) ;  { 102}  ;  and  the  brachy  dome  d  = 
(a>a:b-.c);  {on}. 

FIG.  72. 


FIG.  73. 


FIG.  75. 


FIG.   76. 


FIG.  74. 


FIG.  77. 


All  of  these  are  shown  in  Fig.  77.  Fig.  76  contains  also  the 
brachy  pinacoid  £and  Fig.  74  the  macro  pinacoid  a.  Figs.  72,  73 
and  75  are  simpler  combinations  of  the  same  forms. 

Topaz.  —  Axes  d-.'S-.c—  0.528  :  i :  0.477. 


FIG.  78. 


FIG.  79. 


FIG.  80. 


Fig.  78  shows  the  unit  pyramid  /,  unit  prism  ;«,  brachy  prism 
I  =  (2$  :~b :  <x>  c} ;    {120};   and  the  brachy  dome  /=(cotf:  b:  2c]  ; 


ORTHORHOMBIC  SYSTEM.  35 

{021}.  Fig.  79  shows  the  same  forms  with  the  basal  pinacoid  c 
and  Fig.  80  shows  all  of  79  and  also  two  other  pyramids  t»(4:7: 
§<:);  {223};  q=.(d\b  :  2<r) ;  {221};  and  two  macro-domes  h  = 
(a:a>&:$c);  {203} ;  and  k=  (a  :  oo  ~b  :  2r);  {201}. 


OTHER   CLASSES   OF   THE  ORTHORHOMBIC   SYSTEM. 

6.  CLASS  OF  THE  RHOMBIC  SPHENOID.  —  With  three  axes  of  two- 
fold symmetry  at  90°  to  each  other.      Examples  —  Epsomite  and 
goslarite. 

7.  HEMIMORPHIC  CLASS. — With  two  planes  of  symmetry  at  90° 
to  each  other,  intersecting  in  an  axis  of  two-fold  symmetry.      Ex- 
amples— Calamine,  stephanite  and  prehnite. 


CHAPTER  V. 


TETRAGONAL  SYSTEM.* 

IN  all  Tetragonal  forms  the  crystallographic  axes  can  be 
chosen  at  right  angles  to  each  other  and  so  that  two  will  be  inter- 
changeable, that  is  will  be  surrounded  by  exactly  the  same  number 
of  faces  and  with  corresponding  faces  at  the  same  angles.  The 
grouping  of  faces  about  the  third  axis  will  not  be  the  same  as  to 
angles  and  not  necessarily  the  same  as  to  number  of  faces. 
Series. 

A  substance  can  only  occur  in  forms  of  one  class  and  in  forms 
of  one  series  in  that  class. 

Because  of  the  two  interchangeable  axes  the  intercepts  of  any 
face  upon  these  will  be  simple  multiples  of  each  other.  The  inter- 
cept upon  the  vertical  axis  will  bear  no  simple  relation  to  these  but 
when  two  different  faces  are  compared  there  will  be  found  a  simple 
relation  between  the  corresponding  intercepts  of  all  three  axes. 

Thus  for  zircon  the  common  forms  are  p,  m,  u  and  x  of  Figs.  89  to  92.  For  these 
the  intercepts  and  the  symbols,  if/  be  taken  as  the  unit,  are  : 

/  I  :  I  10.64  =  a  'a  -f  >         I111} 

m  I  :  I  :  co      =  a  :  a  :  m  c  ;  {1 IO} 

u  l:i:i.92  =  a:a:jc;      {331} 

x  I  :3:I.92  =  a:j«:jf  ;    {311} 

CLASS   OF   THE   DITETRAGONAL   PYRAMID.     15. 

No.  1 8.     Holohedry,  Liebisch.     No.  6.     Normal,  Dana. 

Symmetry  of  the  Class. 

Forms  in  this  class  are  symmetrical  to  one  conventionally  hori- 
zontal plane  and  to  four  vertical  planes  at  forty-five  degrees  to  each 
other,  Fig.  81.  The  intersections  of  these  planes  with  each  other 
are  axes  of  symmetry  and  of  these  CC  is  an  axis  of  fourfold 
symmetry. 

*  Also  called  Pyramidal,  Viergliedrige,  Zwei-und-einaxige,  Monodimetric,  Quadratic 
and  Dimetric. 

36 


TETRAGONAL   SYSTEM. 


37 


Choosing  Crystallographic  Axes. 

The  axis  of  fourfold  symmetry  is  chosen  as  the  vertical  axis 
c  and  either  pair  of  alternate  horizontal  axes  as  the  interchange- 
able axes  a. 


FIG.  81. 


FIG.  82. 


Tabulation  of  the  Seven  Type  Forms. 

NAME.  FACES.      WEISS.        MILLER. 
Each  face  oblique  to  c. 

1.  DITETRAGONAL  PYRAMID.  16  a:na:mc  {hkl\ 

2.  PYRAMID  OF  SECOND  ORDER.  8  a  :  oo  a  :  me  {hoi} 

3.  PYRAMID  OF  FIRST  ORDER.  8  a:  a:  me  {hhl\ 
Each  face  horizontal. 

4.  BASAL  PINACOID.  2  co  a  \  co  a  :  c  {001} 
Each  face  vertical. 

5.  DlTETRAGONAL  PRISM.  8  a  :  no.  :  oo  c  {hko} 

6.  PRISM  OF  SECOND  ORDER.  4  a  :  oo  a  :  oo  c  {100} 

7.  PRISM  OF  FIRST  ORDER.  4  a  :  a  :  oo  c  '  {no} 

Description  of  the  Type  Forms. 

1.  DlTETRAGONAL    PYRAMID. a  \  na  \  1HC  J      {kkl}. 

Sixteen  faces,  Fig.  82,  each  cutting  the  two  basal  axes  at  un- 
equal but  simply  proportionate  distances,  and  the  vertical  axis  at  a 
distance  not  simply  proportionate  to  the  other  distances.  In  the 
ideal  forms  the  faces  are  scalene  triangles. 

2.  PYRAMID  OF  SECOND  ORDER.  — a  :  co  a  :  mc\   {hoi}. 

Eight  faces,  Fig.  84,  each  parallel  to  one  horizontal  axis,  and 
cutting  the  other  and  the  vertical  axis  at  distances  not  simple 
multiples  of  each  other.     In  ideal  forms  the  faces  are  isosceles 
triangles. 
•  3.  PYRAMID  OF  FIRST  ORDER.  — a  :  a  :  me ;   {hhl}. 

Eight  faces,  Fig.  83,  each  cutting  the  horizontal  axes  at  equal 
distances,  and  the  vertical  axis  at  a  distance  not  a  simple  multiple 


CR  YSTALLOGRAPHY. 


of  the  basal   intercepts.     In  ideal  forms  the  faces  are  isosceles 
triangles. 

Although  there  is  an  arbitrary  choice  of  axes  which  determines  the  order  of  the  pyra- 
mid, yet  a  first  order  unit  a:  a:  c  {ill}  has  not  the  same  angles  as  a  second  order  unit 
a  :  co  a  :  c  {101}.  For  instance  Figs.  83  and  84  represent  these  for  the  mineral  scheelite 
and  Fig.  85  shows  the  same  forms  combined,  but  the  supplement  angle  pp'  ^=  79°  55  J' 
whereas  dd'  =  72°  40^'. 

FIG.  83.  FIG.  84.  FIG.  85. 


4.  BASAL  PINACOID.  —  co  a  :  CD  a:  c;   {001} . 
Two  faces,  each  parallel  to  both  the  horizontal  axes.     The  faces 
c  of  Figs.  86  to  88. 

FIG.  86.  FIG.  87.  FIG.  88. 


•\ 


1% 


5.  DlTETRAGONAL  PRISM. a  '.  11(1  \  CO  C  ; 

Eight  faces,  each  parallel  to  the  vertical  axis  and  cutting  the 
two  basal  axes  in  distances  unequal  but  simply  proportionate. 
The  faces  s,  Fig.  86. 

The  adjacent  interfacial  angles  can  not  be  equal,  for  then  the  symbol  would  be 
a  :  2.4142  a  :  <x>  c  which  is  opposed  to  the  law  of  rational  intercepts  (Cotangent  22°  3C/ 
=  2.414213). 

6.  PRISM  OF  SECOND  ORDER.  —  a  :  co  a  :  co  c ;    { 100} . 

Four  faces  each  parallel  to  the  vertical  axis  and  to  one  basal 
axis.  The  interfacial  angles  are  90°.  The  faces  a,  Figs.  87,  90, 
94,  etc. 


TETRAGONAL   SYSTEM. 


39 


7.   PRISM  OF  FIRST  ORDER.  —  a:a:coc;   {no}. 

Four  faces,  each  parallel  to  the  vertical  axis  and  cutting  the 
basal  axes   at  equal   distances  from  the  center.     The  interfacial 
angles  are  90°.     The  faces  m,  Figs.  88,  89,  90,  etc. 
Series  and  Combinations  in  the  Class  of  Ditetragonal  Pyramid. 

By  considering  the  forms  of  each  substance  separately,  a  clear 
idea  is  obtained  as  to  the  pyramidal  forms,  which  vary  in  shape 
and  angle  with  the  relative  lengths  of  me  and  a,  although  as  ex- 


FIG.  89. 


FIG.  90. 


FIG.  91. 


FIG.  92. 


plained,  p.  36,  the  pyramids  which  occur  upon  crystals  of  any  one 
substance  are  definitely  related  in  axial  intercepts  and  usually  very 
limited  in  number. 

Zircon. — Axes  a  :  c  =  i  :  0.640. 

Fig.  89  shows  the  common  association  of  unit  pyramid  p  and 
unit  prism  m.  In  Fig.  90  these  two  forms  are  combined  with  the 
prism  of  the  second  order  a  and  in  Fig.  9 1  with  the  pyramid  u  = 
(a  :  a  :  3^) ;  {331}.  Fig.  92  shows  the  union  of  second  order  prism, 
unit  pyramid  and  ditetragonal  pyramid  x  =  (a  :  30  :  3<r) ;  {311}. 


FIG.  93. 


FIG.  94. 


FIG.  95. 


Veswianite. — Axes  a  :  c  =  i  :  0.537. 

The  unit  pyramid  in  vesuvianite  is  only  a  little  flatter  than  in 
zircon,  hence  there  is  little  difference  between  the  pyramid  angles 


4o 


CR  YSTALLOGRAPHY. 


in  Fig.  89  and  Fig.  95.     The  relative  development  of  faces,  or 
"crystal  habit,"  is,  however,  markedly  different. 

Fig.  93  shows  the  combination  of  unit  pyramid  /,  unit  prism  m 
and  basal  pinacoid  c,  Fig.  94  shows  these  three  forms  combined 
with  the  prism  of  the  second  order  a  and  Fig.  95  shows  the  two 
prisms  and  the  unit  pyramid. 


FIG.  96. 


FIG. 


FIG.  99. 


FIG.  97. 


Apophyllite. — Axes  a  :  c  =  i  :  1.252. 

As  indicated  by  the  ratios  of  a  to  c  the  unit  pyramid  of  this 
mineral  is  much  more  acute  than  in  zircon  and  vesuvianite,  this  is 
clearly  apparent  in  Fig.  99.  The  figures  also  illustrate  well  the 
possibility  of  great  differences  in  habit  without  any  difference  in 
occurring  forms,  thus  Figs.  96,  97  and  98  are  all  combinations 

FIG.  100. 


the  unit  pyramid  /,  basal  pinacoid  c  and  second  order  prism  a 
In  Fig.  99  the  basal  pinacoid  does  not  occur. 

Cassiterite.  — Axes  a  :  c  =  i  :  0.6723. 

In  this  the  ratio  of  a  to  c  is  closely  as  in  zircon  but  the  common 


TETRAGONAL   SYSTEM.  41 

association  is  now  the  unit  pyramid  /  with  the  second  order  pyra- 
mid d  as  shown  in  Fig.  100. 

In  Fig.  101  these  forms  occur  with  a  ditetragonal  pyramid  s  = 
(a  :  |  a  :  3<r)  {321}  and  the  unit  prism  m. 


OTHER  CLASSES  OF  SYMMETRY  IN  THE  TETRAGONAL  SYSTEM. 

Six  other  classes  of  symmetry  have  been  distinguished  in  the 
Tetragonal  system  : 

9.  CLASS  OF  THE  THIRD  ORDER  BISPHENOID.  —  With  one  axis 
of  two-fold  symmetry.      No  examples  are  known. 

10.  CLASS  OF  THE  TETRAGONAL  PYRAMID  OF  THIRD  ORDER. — 
With  one  axis  of  four-fold  symmetry.      Example  —  Wulfenite. 

1 1.  SCALENOHEDRAL  CLASS.  —  With  two  planes  of  symmetry  at 
90°  intersecting  in  an  axis  of  four-fold  symmetry.     Also  two  axes 
of  two-fold  symmetry  midway  between  the  planes.      Examples  — 
Chalcopyrite  and  stannite. 

1 2.  TRAPEZOHEDRAL  CLASS.  —  Without  planes  of  symmetry,  but 
with  one  four-fold  axis  at  90°  to  four  two-fold  axes.      No  exam- 
ples among  minerals  are  known,  the  type  salt  is  nickel  sulphate, 
NiS04-6H2O. 

13.  CLASS  OF  THE  TETRAGONAL  PYRAMID  OF  THIRD  ORDER. — 
With  one  horizontal  plane  of  symmetry  and  one  vertical  axis  of 
four-fold  symmetry.      Examples  —  Scheelite,  wernerite  and  stolzite. 

14.  CLASS  OF  THE  DITETRAGONAL  PYRAMID. — With  four  planes 
of  symmetry  intersecting  in  an  axis  of  four-fold  symmetry.      No  ex- 
amples among  minerals  are  known.     An  example  in  salts  is  lodo- 
succinimid,  C4H4O2NI. 


CHAPTER   VI. 


HEXAGONAL  SYSTEM.* 

ALL  hexagonal  crystals  are  conveniently  referred  to  four  crys- 
tallographic  axes,  one  vertical  and  at  right  angles  to  the  others, 
three  horizontal  and  interchangeable  and  at  sixty  degrees  to  each 
other. 

Twelve  classes  of  symmetry  are  recognized  which  fall  naturally 
in  two  divisions : 

The  Rhombohedral  Division^  including  seven  classes,  each  with 
an  axis  of  three-fold  symmetry. 

The  Hexagonal  Division,  including  five  classes,  each  with  an  axis 
of  six-fold  symmetry. 

RHOMBOHEDRAL   DIVISION,    SCALENOHEDRAL   CLASS. 

No.  13.    Rhombohedral  Hemihedry,  Liebisch.     No.  19.    Rhombohedral  Group,  Dana. 

This  most  important  group  in  the  hexagonal  system  includes 
the  crystals  of  such  minerals  as  calcite,  corundum,  hematite  and 
chabazite.  All  crystals  in  the  class  are  symmetrical  to  three  planes 


FIG.  102. 


FIG.  103. 


FIG.  104. 


at  60°  to  each  other,  Fig.  102.     Their  intersection  is  the  three-fold 
axis  and  there  are  three  two-fold  axes  OA  diagonal  to  the  planes. 

*  Also  called  Rhombohedral,  Sechsgliedrige,  Drei-und-Einaxige  and  Monotrimetric. 
fThe  "  rhombohedral  division"  is  referred  by  Miller  to  three  oblique  axes. 
42 


HEXAGONAL   SYSTEM.  43 

Choosing  Crystallographic  Axes. 

The  axes  of  symmetry  are  chosen.     The  three-fold  axis  is  the 
vertical,  r,  the  others  are  horizontal  and  one  of  them  is  placed  from 
left  to  right. 
Tabulation  of  the  Seven  Type  Forms. 

NAME.  FACES.          WEISS.  MILLER. 
Each  face  oblique  to  c. 

1.  SCALENOHEDRON.  12  a :  na  :pa  :  me  {hkll} 

2.  HEXAG.  PYRAMID  2°  ORDER.  12  2a:2a  \a\mc  {h-h-zh-l} 

3.  RHOMBOHEDRON  i°  ORDER.  6  a  :  oo  a  :  a  :  me  {hohl} 
Each  face  perpendicular  to  c. 

4.  BASAL  PINACOID.  2  co  a  -.  oo  a  :  oo  a\c      {0001} 
Each  face  parallel  to  c. 

5.  DIHEXAGONAL  PRISM.  12  a '  :  na  : pa  :  co  c  {hkto} 

6.  HEXAG.  PRISM  2°  ORDER.  6  2a  :  2a  :  a  :  co  c  {1120} 

7.  HEXAG.  PRISM  i °  ORDER.  6  a:  <&  a  :a  :  <oc  jioTo} 

Description  of  the  Type  Forms. 

1 .  SCALENOHEDRON.  —  a  :na  :  pa*  \  me  ;    {hkll} . 

Twelve  faces,  each  cutting  all  the  axes.  In  the  ideal  form  the 
faces  are  scalene  triangles.  The  adjacent  polar  edges  are  neces- 
sarily unequal. 

Fig.  103.     Also  the  faces  v,  Figs.  113  and  116. 

2.  HEXAGONAL  PYRAMID  OF  SECOND  ORDER.  —  20.  :  2a  :  a  :  me ; 
{h  -h-ili-i}. 

Twelve  faces,  Fig.  104,  each  cutting  one  horizontal  axis  at  a 
certain  distance,  the  others  at  twice  f  that  distance,  and  the  vertical 
axis  at  some  distance  not  simply  proportionate  p-IGt 

to  the  rest.     In  the  ideal   form  the  faces  are 
isosceles  triangles. 

3.  RHOMBOHEDRON   OF  FIRST  ORDER.  —  a  : 
co  a  :a  \mc;   {/toki}. 

Six  faces,  each  cutting  two  basal  axes  at  equal 
distances,  parallel  to  the  third  and  cutting  the 
vertical.     In  the  ideal  forms  the  faces  are  rhombs,  Figs.  105,  109, 
1 10  and  1 14. 

4.  BASAL  PINACOID. — coa  :coa  :coa  :  c  ;   {oooi}. 

Two  faces  each  parallel  to  the  three  horizontal  axes.  The  faces 
c  of  Figs.  1 06  to  1 08. 

*  It  may  be  shown  that  in  the  Weiss  symbols  the  numerical  value  of  /  =  n  \  n  —  I 
and  in  the  Miller  symbols  that  »  =  —  (/&  +  £). 

f  Easily  shown  by  the  angles  in  a  horizontal  section. 


44 


CR  YSTALL  OGRAPH  Y. 


5.  DIHEXAGONAL  PRISM. — a  \  na  :  pa  :  oo  c  ; 

Twelve  faces  each  parallel  to  the  vertical  axis  and  cutting  all  hori- 
zontal axes  at  unequal  distances,  simple  multiples  of  each  other, 
Fig.  1 06,  shows  .y  =  (a  :  |«  :  3^  :  co<:) ;  {2130}. 

6.  HEXAGONAL  PRISM   OF  SECOND   ORDER.  —  20.  :  20.  :  a  :  oo  c ; 

{I  120}. 

Six  faces  each  parallel  the  vertical  axis  and  cutting  one  horizontal 
FIG.  106.  FIG.  107.  FIG.  108. 


axis  at  a  certain  distance,  the  other  two  at  twice  that  distance.     The 
faces  <?,  Figs.  107  and  121. 

7.  HEXAGONAL  PRISM  OF  FIRST  ORDER.  — a  :  coa  :  a  :  oor; 
{1010}. 

Six  faces  each  parallel  to  the  vertical  and  one  horizontal  axis  and 
cutting  the  other  two  at  equal  distances.     The  faces  m,  Figs.  108, 
1 12  and  115. 
Combinations  in  the  Scalenohedral  Class. 

Calcite.  —  Axes  a  :  c  =  i  :  0.854. 

Figs.  109  to  116  represent  the  more  common  of  the  extremely 
numerous  forms  of  calcite.  Rhombohedrons  and  scalenohedrons 
predominate.  The  rhombohedrons  shown  are  p  the  unit,  Fig. 
109,  e  the  negative  form  of  a  :  coa  :  a  :  ±c  ;  { 1012}  ;  Fig.  1 10  ;  / 
the  negative  form  of  a:  coa:a:2c;  {2021},  Fig.  114;  and  q 
the  positive  form  of  a  :  coa  :  a  :  \6c  ;  { 16.0. 16. 1 }  ;  Fig.  1 1 1. 

Two  scalenohedrons  only  are  shown,  v  =  (%a  :  $a  :  a  :  3<r) ; 
{2131};  Fig.  113,  and  w  =  (|a  :  4*  :  a:  ±r);  {3145};  Fig.  116. 

The  rhombohedron  e  occurs  mpre  frequently  than  the  unit  and 
is  shown  in  combination  with  the  rhombohedron  q  in  Fig.  1 1 1  and 
with  the  prism  m  in  Figs.  1 1 2  and  115. 

The  unit  rhombohedron  is  shown  in  combination  with  the  sca- 
lenohedron  v  in  Fig.  113,  and  with  the  two  scalenohedrons  v  and 
w  in  Fig.  1 1 6. 


HEXAGONAL   SYSTEM. 
FIG.  109.  FIG.  1  10. 


45 


FIG.  in. 


FIG.  112. 


FIG.  113. 


FIG.  114. 


Hematite.  — Axes  a  :  c  —  i  :  1.365. 

Fig.  1 1 7  shows  the  unit  rhombohedron  /  with  the  basal  pina- 
coid  c  and  the  second  order  pyramid  n  =  (2a  :  2<z  :  a  :  -|f) ;  (2243 }  ; 
FIG.  115.  FIG.  116. 


Fig.  1 19  shows  the  same  except  that  the  basal  pinacoid  is  replaced 
by  the  rhombohedron  £•=  (a  :  coa  :a:  ^<r);  {1014};  and  Fig.  118 
shows  the  two  rhombohedrons  p  and  g. 

FIG.  117.  FIG.  118.  FIG.  119. 


Corundum.  — Axes  a  :  c  =  i  :  1.363. 

The  unit  forms  of  hematite  and  corundum  are  practically  identical, 


46 


CR  YSTALL  OGRAPHY. 


but  the  combinations  and  habit  are  very  different.     Fig.  1  20  shows 


a  second  order  pyramid  n  =  (2a  :  2a  :  a  : 


2243}.      Fig.  121 


shows  this  and  two  other  second  order  forms  o  =  (2a  :  2a  :  a  :  |cV 

_  __  \  3    /  ' 

{4483};  and  a  =  (2a  :  2a  :  a  :oor);  {1120};  and  a  rhombohedron 
f=(a:coa:a:2c);  {2021}.  Fig.  122  shows  a  second  order 
pyramid  w  =  (20.  :  2a  :  a  :  2c)  ;  {1121};  with  the  unit  rhombohe- 
dron /  and  the  basal  pinacoid  c. 


FIG.  120. 


FIG.  121. 


FIG.  122. 


RHOMBOHEDRAL  DIVISION,  HEMIMORPHIC  CLASS.*     20. 

No.  14.     Second  Hemimorphic  Tetartohedry,  Liebisch.     No.  20.     Rhombohedral 
Hemimorphic  Group,  Dana. 

The  common  mineral,  tourmaline,  and  the  ruby  silvers,  proustite 
and  pyrargyrite,  occur  in  forms  showing  different  groupings   of 
FIG.  123.  FIG.  124. 


faces  at  opposite  ends  of  the  vertical  axis.     That  is  the  forms  are 
symmetrical  to  a  three-fold  axis  and  to  three  planes  through  this  at 
60°  to  each  other,  Fig.  123. 
Choosing  Crystallographic  Axes. 

The  three -fold  axis  is  taken  as  the  vertical  (c)  axis,  the  others  lie 
in  the  planes  of  symmetry. 

*  The  forms  differ  so  markedly  from  those  of  the  preceding  and  following  class  that 
it  has  been  thought  wise  to  describe  them  in  detail. 


HEXAGONAL  SYSTEM. 


47 


Tabulation  of  Seven  Type  Forms. 

NAME.  FACES.         WEISS.  MILLER. 

Each  face  oblique  to  c. 

\.   HEM.  DITRIGONAL  PYRAMID. 

2.  HEM.  HEX.  PYRAM.  SECOND  ORDER. 

3.  HEM.  TRIGONAL  PYRAM.  FIRST  ORDER.  3 
Each  face  perpendicular  to  c. 

4.  BASAL  PLANE. 
Each  face  parallel  to  c. 

5.  DITRIGONAL  PRISM. 

6.  HEXAG.  PRISM  SECOND  ORDER. 

7.  TRIGONAL  PRISM  FIRST  ORDER. 

Description  of  the  Type  Forms. 

1.  HEMIMORPH.  DITRIGONAL  PYRAMID. — a  :  na\pa  :  me;  {hkll}. 
Six  faces,  Fig.  124,  each  cutting  all  horizontal  axes  at  simply 

related  distances  and  all  cutting  the  vertical  axis. 

2.  HEMIMORPH.  HEXAG.  PYRAMID  2°  ORDER.  —  20.  :  20.  :  a  :  me; 
[kh -2/1-1}. 

Six  faces,  Fig.  125,  each  cutting  one  horizontal  axis  at  a  certain 
distance,  the  others  at  twice  that  distance,  and  the  vertical  axis  at 
a  distance  not  simply  proportionate. 


6 

a  : 

na  :pa  : 

me 

{hkil± 

3 

2a 

:  2a  :  a  : 

me 

3 

a  : 

co  a  :  a  : 

me 

{holil  } 

i 

CO 

a  :  coa  : 

co  a  :  c 

{0001} 

6 

a  : 

na  :pa  : 

CO   £ 

{hkio} 

6 

20. 

\2a:a: 

CO  £ 

{1120} 

3 

a  : 

co  a  :  a 

:  co  c 

{1010} 

FIG.  125. 


FIG.  126. 


3.  HEMIMORPH.   TRIGONAL   PYRAMID    i°    ORDER. — a  :  co  a  : 
a  :  me;  {holil}. 

Three  faces,  Fig.  1 26,  each  parallel  to  one  horizontal  axis,  cutting 
the  other  two  at  equal  distances,  and  the  vertical  axis  at  some  dis- 
tance not  simply  proportionate. 

4.  THE  BASAL  PLANE.  —  co  #  :  co  a:  co  a\c;   (oooi  }. 
One  face  parallel  to  the  basal  axes. 

5.  DITRIGONAL  PRISM. — a  \na\pa\  co  c;   {hkio}. 

Six  faces,  Fig.  127,  each  parallel  to  the  vertical  axis  and  cutting 
all  horizontal  axes  at  unequal  distances  simple  multiples  of  each 
other. 

6.  HEX.  PRISM  OF  SECOND  ORDER. — 2a:  2a:a:  coc;  {h-h-2h-o}. 
Previously  described.     See  Fig.  107. 

7.  TRIGONAL  PRISM  OF  FIRST  ORDER. — a  :oo«:«:oor;{ioio}. 


48 


CR  YSTALLOGRAPHY. 


Three  vertical  faces,  each  parallel  to  one  horizontal  axis  and  in- 
tersecting the  others  at  equal  distances  from  the  center,  Fig.  128. 


FIG.  127. 


FIG.  128. 


Combinations  in  the  Hemimorphic  Class. 

Tourmaline. — Axes  a  :  c=  i  :  0.447. 

Fig.  129  shows  the  first  order  trigonal  prism  m,  the  second 
order  hexagonal  prism  a ;  at  the  upper  end  the  trigonal  pyramids 
of  first  order/  =  (a  :  oo  a  :  a  :  r);  { 101 1);  and/=  (a  :  oo  a  :  a  :  2c] 
{2021 };  but  at  the  lower  end  the  trigonal  pyramid  /  only.  Fig, 
1 30  shows  m,  p  and  a,  but  does  not  so  evidently  reveal  the  hemi- 
morphic  symmetry.  Fig.  1 3 1  again  shows  m  and  a  central,  with 
at  one  end  p  and  at  the  other/". 

FIG.  129.  FIG.  130.  FIG.  131. 


\ 


OTHER  CLASSES  OF  SYMMETRY  IN  THE  RHOMBOHEDRAL  DIVISION. 
In  each  there  is  an  axis  of  three-fold  symmetry. 

1 6.  CLASS  OF  HEMIMORPH.  TRIGONAL  PYRAMID  3°  ORDER. 
The  three -fold  axis.    No  planes  or  center  of  symmetry.    Example 

sodium  periodate,  NaIO4-3H2O. 

17.  CLASS  OF  RHOMBOHEDRON  3°  ORDER. 

The  three-fold  axis  and  center  of  symmetry.    Examples  —  Dolo- 
mite, ilmenite,  willemite,  phenacite,  dioptase. 


HEXAGONAL   SYSTEM. 


49 


1 8.  CLASS  OF  TRIGONAL  TRAPEZOHEDRON. 

The  three-fold  axis  and  three  two-fold  axes  of  symmetry  at  90° 
thereto.      Examples  —  Quartz,  cinnabar. 

19.  CLASS  OF  TRIGONAL  PYRAMID  3°  ORDER. 

The  three-fold  axis  and  one  plane  of  symmetry  at  90°  thereto. 
No  examples  known. 

22.  CLASS  OF  DlTRIGONAL  PYRAMID. 

The  three-fold  axis,  three  planes  at  60°  and  one  at  90°  to  the 
three.     No  examples  known. 


HEXAGONAL  DIVISION.     CLASS   OF   DIHEXAGONAL   PYRAMID.     27. 

No.  6.   Holohedral,  Liebisch.     No.  13.   Normal  Group,  Dana. 

A  few  minerals,  notably  beryl,  crystallize  in  forms  symmetrical 
to  one  horizontal  plane  and  to  six  vertical  planes  at  thirty  degrees 
to  each  other  and  to  one  six-fold  and  six  two-fold  axes  which  are 
the  lines  of  intersection  of  these  planes,  Fig.  132. 

Choosing  Crystallographic  Axes. 

The  six-fold  axis  is  chosen  as  the  vertical  c,  the  two-fold  axes  as 
the  horizontal  axes  a,  one  of  which  is  conventionally  placed  from 
left  to  right. 

Tabulation  of  the  Seven  Type  Forms. 

FACES. 


WEISS. 


MILLER. 


NAME. 
Each  face  oblique  to  c. 

1.  DIHEXAGONAL  PYRAMID. 

2.  HEXAG.  PYRAMID  2°  ORDER. 

3.  HEXAG.  PYRAMID  i°  ORDER. 
Each  face  perpendicular  to  c. 

4.  BASAL  PINACOID. 
Each  face  parallel  to  c, 

5.  DIHEXAGONAL  PRISM. 

6.  HEXAG.  PRISM  2°  ORDER. 

7.  HEXAG.  PRISM  i°  ORDER. 

Description  of  the  Type  Forms. 

i.  DIHEXAGONAL  PYRAMID.  - 

Twenty-four  faces,  Fig.  133,  each  of  which  cuts  the  three  hori- 
zontal axes  at  unequal  distances,  simple  multiples  of  each  other ; 
and  the  vertical  axis  at  some  distance  not  simply  related  to  the 
others.     In  the  ideal  form  the  faces  are  scalene  triangles. 
4 


24         a  :  na  \pa 
12          2a:2a:a 
12         a  :  co  a  :  a 

me 
me 
me 

{hkll} 

{h-hih-l} 
{kohl} 

2          co  a  :  co  a 

co  a  :c 

{0001} 

12         a  :  na  :  pa 
6         2a  :  2a  :  a 
6         a  :  oo  a  :  a 

COC 

oo  c 

CO   C 

{Atio} 

{1120} 

{1010} 

z  :  na  \pa  :  me 

\hkll}. 

CR  YSTALLOGRAPHY. 


2.  HEXAGONAL  PYRAMID  OF  SECOND  ORDER.  —  See  Fig.  104. 

3.  HEXAGONAL  PYRAMID  OF  FIRST  ORDER. — a  :  co  a  :  a  :  me; 
{kohl}. 

Twelve  faces,  Fig.  1 34,  each  parallel  to  one  horizontal  axis,  cutting 
the  others  at  equal  distances,  and  the  vertical  axis  at  some  distance 
not  simple  proportionate.  In  ideal  forms  the  faces  are  isosceles 
triangles. 

4.  BASAL  PINACOID.  —  The  faces  c  of  Figs.  135  to  137. 

5.  DIHEXAGONAL  PRISM.  —  See  Fig.  1 06. 


FIG.  132. 


FIG.  133. 


FIG.  134. 


6.  HEXAGONAL  PRISM  OF  SECOND  ORDER. — See  Fig.  107. 

7.  HEXAGONAL  PRISM  OF  FIRST  ORDER.  —  See  Fig.  108  or  the 
faces  m  of  Figs.  135  to  137. 

Combinations  in  the  Class  of  Dihexagonal  Pyramid. 
Beryl. — Axes  a  :  c  =  i  :  0.499. 


FIG.  135. 


FIG.  136. 


FIG.  137. 


Fig.  135  shows  the  prism  of  first  order  m  and  basal  pinacoid  c ; 
in  Fig.  1 36  the  second  order  pyramid  c  =  (20.  :  ia  :  a  :  2c] ;  { 1 1 2 1 } ; 
occurs  and  in  Fig.  137  the  unit  pyramid  /  is  also  present. 


HEXAGONAL   SYSTEM.  5  I 

OTHER  CLASSES  IN  THE  HEXAGONAL  DIVISION. 
Each  with  an  axis  of  six-fold  symmetry. 

23.  CLASS  OF  THIRD  ORDER  HEXAGONAL  PYRAMID. — The  six- 
fold axis  only.      Example — nephelite. 

24.  CLASS  OF  HEXAGONAL  TRAPEZOHEDRON.  — The  six-fold  axis 
and  six  2-fold  axes  of  symmetry  at  90°  thereto.       Example  — 
Barium-antimonyl    dextro-tartrate   potassium    nitrate,    Ba(SbO)2- 
(C4H406)2-KN03. 

25.  CLASS  OF  THIRD  ORDER  HEXAGONAL  PYRAMID.  — The  six- 
fold axis  and  a  plane  of  symmetry  at  90°  thereto.      Examples  — 
Apatite,  pyromorphite,  mimetite,  vanadinite. 

26.  CLASS  OF  HEMIMORPHIC  DIHEXAGONAL  PYRAMID.  —  The  six- 
fold axis  and  six  planes  of  symmetry  at  30°  to  each  other  inter- 
secting therein.     Example  —  lodyrite. 


CHAPTER   VII. 

ISOMETRIC  SYSTEM. 

THE  Isometric*  system  includes  all  crystal  forms  which  can  be 
referred  to  three  interchangeable  axes  at  right  angles  to  each  other, 
that  is  axes  about  which  there  are  equal  numbers  of  faces  grouped 
with  corresponding  faces  at  the  same  angles. 

Five  classes  are  distinguished,  of  which  three  include  nearly  all 
known  isometric  minerals. 

HEXOCTAHEDRAL  CLASS.     32. 

No.  I.   Holohedral,  Liebisch.     No.  i.   Normal  Group,  Dana. 

Symmetry  of  the  Class. 

There  are  three  planes  of  symmetry,  Fig.  138,  parallel  to  cube 
laces,  and    six  planes    through  diagonally  opposite   cube  edges. 
There  are  also,  Fig.   139,  three  four-fold,  four  three-fold  and  six 
two-fold  axes  of  symmetry. 
Choosing  Crystallographic  Axes. 

The  three  axes  of  four-fold  symmetry  are  chosen  as  the  crystal - 
lographic  axes.  Usually  one  is  assumed  to  be  vertical  and  one  to 
extend  from  left  to  right. 

Tabulation  of  the  Seven  Type  Forms. 

NAME.  FACES.            WEISS.  MILLER. 
Each  face  intersects  all  axes. 

1.  HEXOCTAHEDRON.  48  a:na:ma  {hkl} 

2.  TRAPEZOHEDRON.  24  a:  ma:  ma  {hkk} 

3.  TRISOCTAHEDRON.  24  a:  a:  ma  {hhl} 

4.  OCTAHEDRON.  8  a: a: a  {m} 
Each  face  parallel  to  one  axis. 

5.  DODECAHEDRON.  12  a:  a:  ma  {no} 

6.  TETRAHEXAHEDRON.  24  a  :  na  :  oo  a  {hko} 
Each  face  parallel  to  two  axes. 

7.  CUBE.  6  a:  03  a:  ma  {100} 

Description  of  the  Type  Forms. 

i.   HEXOCTAHEDRON.  —  a\na\ma;   {hkl}. 

*  Also  called  Tesseral,  Tessular,  Regular,  Cubic  and  Monometric. 


ISOMETRIC  SYSTEM. 


53 


Forty-eight  faces  each  cutting  the  three  axes  in  three  different, 
but  simply  proportionate  distances.  In  the  ideal  forms  the  faces 
are  scalene  triangles.  Fig.  140  shows  a  :  |#  :  $a ;  {321}. 


FIG.  138. 


FIG.  139. 


The  small  black  squares  and  triangles  indicate  axes  of  four-fold  and  three-fold  sym- 
metry respectively. 

2.  TRAPEZOHEDRON.  —  a  :  ma  :  ma  ;  {hkk}. 
Twenty-four  faces,  each  cutting  two  axes  equally  and  the  third 
in  some  shorter  distance  bearing  a  simple  ratio  to  the  others.     In 


FIG.  140. 


FIG.  141. 


FIG.  142. 


FIG.  143. 


the  ideal  form  the  faces  are  trapez  urns.     Fig.  141  shows  a  :  2a  :  2a  ; 

{211}. 

3.  TRISOCTAHEDRON. — a  :  a    ma;  \hhl\. 

Twenty-four  faces,  each  cutting  two  axes  at  equal  distances,  the 
third  axes  at  some   longer  distance  a  simple 
multiple  of  the  others.     In  the  ideal  forms  the 
faces   are  isosceles  triangles.     Fig.  142  shows 
r=  (a  :  a  :  20)  ;  {221}. 

4.  THE  OCTAHEDRON.  —  a  :  a  :  a  ;  {in}. 
Eight  faces,  Fig.  143,  each  cutting  the  three 

axes  at  equal  distances.     In  the  ideal  form  the 
faces  are  equilateral  triangles. 

5.  TETRAHEXAHEDRON.  — a  :  na  :  coa  ;  [hko], 

Twenty -four  faces,  Fig.  144,  each  parallel  to  one  axis  and  cut- 


54 


CR  YSTALL  OGRAPHY. 


ting  the  other  two  unequally  in  distances  bearing  a  simple  ratio  to 
each  other.  In  the  ideal  forms  the  faces  are  equal  isosceles  tri- 
angles. Fig.  144  shows  a  :  2a  :coa;  {210}. 

FIG.  144.  FIG.  145.  FIG.  146. 


6.  THE  DODECAHEDRON.  —  a  :  a  :  coa;  {no}. 

Twelve  faces,  Fig.  145,  each  parallel  to  one  axis  and  cutting  the 
others  at  equal  distances.     In  the  ideal  form  each  face  is  a  rhombus. 

7.  THE  CUBE.  — a  :  oo  a  :  oo  a  ;   { 100}. 


FIG.  147. 


FIG.  148. 


FIG.  149. 


Six  faces,  Fig.   146,  each  parallel  to  two  axes.     In  the  ideal 
forms  the  faces  are  squares. 
Combinations  in  the  Hexoctahedral  Class. 

The  most  frequently  occurring  forms  are  the  cube  a,  the  octahe- 


FIG.  150. 


FIG.  151. 


FIG.  152. 


dron/,  the  dodecahedron  d,  and  the  trapezohedron  n  =  (a  :  2a  :  2a)\ 
{211}.     The  other  forms  usually  occur  modifying  these. 

The  cube  a  and  dodecahedron  d,  Figs.  147,  148,  are  combined 
in  crystals  of  fluorite,  argentite  and  cuprite.     The  cube  and  octa- 


ISOMETRIC  SYSTEM. 


55 


hedron  p,  Figs.  149,  1 50  and  1 5 1,  are  very  frequently  combined  in 
fluorite,  galenite,  silver,  sylvite  and  many  other  minerals.  The 
octahedron,/,  and  dodecahedron,  d,  Figs.  152  and  153,  are  fre- 
quently found  in  spinel,  magnetite,  franklinite  and  cuprite,  while 

FIG.  154. 


FIG.  153. 


FIG.  155. 


the  three  together,  cube,  dodecahedron  and  octahedron,  Fig.  1 54, 
occur  fn  smaltite,  galenite  and  fluorite.  The  tetrahexahedron  e  = 
(a  :  2a  :  co  «);  {210}  ;  is  found  with  the  cube  in  fluorite,  Fig.  155. 

FIG.  156.  FIG.  157.  FIG.  158. 


The  trapezohedron  n  =  (a  :  2a:  20) ;  {211}  ;  is  common  in  analcite, 
garnet  and  amalgam,  either  combined  with  the  dodecahedron,  Figs. 
156  and  158  or  with  the  cube,  Fig.  157. 


FIG.  160. 


FIG.  161. 


Another  trapezohedron  o  =  (a  :  ^a  :  30) ;  {311};  occurs  in  spinel 
and  magnetite  either  with  the  octahedron,  Fig.  1 59,  or  with  both 
octahedron  and  dodecahedron,  Figs.  160  and  161. 

The  trisoctahedron  r  —  (a  :  a  :  20) ;  (221 }  ;  occasionally  occurs, 
especially  in  galenite  and  magnetite,  combined  with  octahedron 


CR  YSTALLOGRAPHY. 


and  dodecahedron,  Fig.  162.  The  hexoctahedron  t=(a  '.2a  :  4.0)  ; 
{421}  ;  occurs  modifying  cubes  of  fluorite,  Fig.  163,  and  another 
hexoctahedron  s=  (a  :  ^a  :  3^)  ;  {321 }  ;  occurs  in  garnet,  Fig.  164. 


FIG.  162. 


FIG.  163. 


FIG.  164. 


HEXTETRAHEDRAL   CLASS.     31. 
No.  2.  Tetrahedral  Hemihedry,  Liebisch.     No.  3.  Tetrahedral  Group,  Dane. 


FIG.  165. 


In  this  class  of  isometric  forms,  to  which 
crystals  of  the  diamond,  tetrahedrite,  spha- 
lerite and  boracite  belong,  the  shaded  planes 
of  Fig.  138  are  no  longer  planes  of  sym- 
metry, and  the  symmetry  is  restricted  to 
the  diagonal  planes  shown  in  Fig.  165  and 
to  the  four  three-fold  and  three  two-fold 
axes  formed  by  their  intersection. 
Choosing  Crystallographic  Axes. 
The  three  axes  of  two-fold  symmetry  are  chosen  as  the  crystallo- 
graphic  axes. 

Tabulation  of  the  Seven  Type  Forms. 

NAME.  FACES.  WEISS.              MILLER. 
Each  face  intersects  all  axes. 

1.  HEXTETRAHEDRON.  24  a:na:ma 

2.  TRISTETRAHEDRON.  12  a:  ma:  ma 

3.  DELTOHEDRON.  12  a:  a:  ma               \hhl\ 

4.  TETRAHEDRON.  4  a  :  a  :  a                  { 1 1 1 } 
Each  face  parallel  to  one  axis. 

5.  TETRAHEXAHEDRON.  24  a  :  na :  oo  a           {hko} 

6.  DODECAHEDRON.  12  a:a:coa              {no} 
Each  face  parallel  to  two  axes. 

7.  CUBE.  6  a  :  oo  a  :  oo  a           {100} 

Descriptions  of  the  Type  Forms. 

i .   HEXTETRAHEDROX.  —  a  :  na  :  ma ;   [kkl] . 

Twenty-four  faces  each  cutting  the  three  axes  in  three  different, 


ISOMETRIC  SYSTEM.  57 

but  simply  proportionate,  distances.     In  the  ideal  forms  the  faces 
are  scalene  triangles.     Fig.  166. 

2.  TRISTETRAHEDRON.  — a  :  ma  :  ma  ;   {hkk}. 

Twelve  faces,  Fig.  167,  each  cutting  two  axes  equally  and  the 


FIG.   1 66.  FIG. 


third  in  some  shorter  distance  bearing  a  simple  ratio  to  the  others. 
In  the  ideal  form  the  faces  are  isosceles  triangles. 

3.   DELTOHEDRON. — a:  a:  ma;   {hhl}. 

Twelve  faces,  each  cutting  two  axes  equally  and  the  third  in 
some  longer  distance  a  simple  multiple  of  the  others.  In  the  ideal 
form  the  faces  are  trapeziums.  Fig.  i68  shows  r  =  (a  :  a  :  2a); 

{221}. 

FIG.   168.  FIG.   169. 


4.  THE  TETRAHEDRON. — a:  a:  a;   {in}. 

Four  faces,  Fig.  169,  each  cutting  the  three  axes  at  equal  dis- 
tances. In  the  ideal  form  the  faces  are  equilateral  triangles. 

5.  TETRAHEXAHEDRON.  —  Fig.  144. 

6.  THE  DODECAHEDRON. — Fig.  145. 

7.  THE  CUBE.  —  Fig.  146. 
Combinations  in  the  Hextetrahedral  Class. 

The  characteristics  of  the  crystals  of  this  group  are  best  shown 
in  combinations  of  forms,  since  the  simple  forms  are  comparatively 
rare  and  the  predominating  form  is  frequently  the  cube. 

The  combination  of  the  positive  and  negative  tetrahedrons,  Fig. 
170  occurs  in  crystals  of  sphalerite  and  tetrahedrite.  The  combi- 


CR  YSTALL  OGRAPHY. 


nation  of  the  tetrahedron  and  cube  a,  Figs.  171  and  172,  is  com- 
mon in  boracite  and  pharmacosiderite.  The  tetrahedron  with  the 
dodecahedron  d,  Fig.  173,  occurs  in  tetrahedrite,  and  with  both 
cube  and  dodecahedron,  Fig.  174,  in  boracite. 


FIG.   170. 


FIG.   171. 


FIG.   172. 


\\J 

!^_ 


Figs.  175  and  176  are  crystals  of  tetrahedrite.  In  Fig.  175  the 
negative  form  of  n  ==•  (a  :  2a  :  2a)  ;  {211};  occurs  and  in  Fig.  1 76 
the  positive  form  of  n  with  the  dodecahedron  d. 


FIG.  173. 


FIG.   174. 


FIG.  175. 


Fig.  177  includes  the  dodecahedron  d,  the  deltohedron  r  =  (a  : 
a  :  20) ;  {221};  and  the  tristetrahedrons  o  =  (a  :  ^a  :  3^) ;  {311}; 
and  n  =  (a  :  2a  :  20);  {211}  ;  Fig.  178  shows  the  hextetrahedron  s 


FIG.  176. 


FIG.   177. 


FIG.   178. 


=  (a  :  f#  :  3^) ;  {321};  combined  with  the   cube  and   tetrahexa- 
hedron  g  —  (a  :  |«  :  oo  a)  ;  (320). 


ISOMETRIC  SYSTEM. 


59 


FIG.  179. 


CLASS   OF   THE   DIPLOID.     30. 

No.  4.   Pentagonal  Hemihedry,  Liebisch.     No.  2.   Pyritohedral  Group,  Dana. 

Symmetry  of  the  Class. 

Crystals  of  the  common  mineral  pyrite 
and  of  the  minerals  cobaltite  and  smaltite 
are  symmetrical  to  three  planes  at  right 
angles  and  to  three  axes  of  two-fold  and 
four  axes  of  three-fold  symmetry,  as 
shown  in  Fig.  179. 
Choosing  Crystallographic  Axes. 

The  three  axes  of  two-fold,  symmetry 
are  chosen  as  the  crystallographic  axes. 
Tabulation  of  the  Seven  Type  Forms. 

WEISS. 


NAME. 
Each  face  intersects  all  the  axes. 

1.  DIPLOID.  a  :  na  :  ma 

2.  TRAPEZOHEDRON.  a {nia  :  m< 

3.  TRISOCTAHEDRON.  a: a: ma 

4.  OCTAHEDRON.  a: a: a 
Each  face  parallel  to  one  axis. 

5.  PYRITOHEDRON.  a:na:a>a 

6.  DODECAHEDRON.  a:  a -.ma 
Each  face  parallel  to  two  axes. 

7.  CUBE.  a  :  co a  :  co a 


MILLER. 

.  {hkl\ 
{hkk} 
{hhl} 
{in} 

[Mo] 

{110} 

{100} 


Description  of  the  Type  Forms. 

i.   DIPLOID.  — a  :  na  :  ma  ;   {hkl}. 

Twenty-four  faces  each  cutting  the  three  axes  in  three  different, 
but  simply  proportionate,  distances.  In  the  ideal  form  the  faces 
are  trapeziums.  Fig.  180  shows  a  positive  form. 

FIG.  180.  FIG.  181. 


2.  TRAPEZOHEDRON,  Fig.  141. 

3.  TRISOCTAHEDRON,  Fig.  142. 

4.  THE  OCTAHEDRON,  Fig.  143. 


60  CR  YSTALL  OGRAPHY. 


5.  PYRITOHEDRON.  —  a  :  na  :  coa; 

Twelve  faces,  Fig.  181,  each  parallel  to  one  axis  and  cutting  the 
other  two  unequally  in  distances  bearing  a  simple  ratio  to  each 
other.  In  the  ideal  forms  the  faces  are  pentagons. 

6.  THE  DODECAHEDRON,  Fig.  145. 

7.  THE  CUBE,  Fig.  146. 
Combinations  in  the  Class  of  the  Diploid. 

FIG.  182.  FIG.  183.  FIG.  184. 


Fig.  182  shows  the  pyritohedron  c  =  (a  :  2a  :  coa) ;  {210};  with 
the  cube  a.  Figs.  183  and  184  show  the  same  form  with  the 
octahedron  p. 

FIG.  185.  FIG.  186  FIG.  187. 


Fig.  185  shows  the  three  forms  combined.  Fig.  186  shows  the 
same  pyritohedron  e  and  octahedron  p  combined  with  the  diploid 
s  =  (a  :  %a  :  3*7)  ;  {321};  and  Fig.  187  shows  this  diploid  with  the 
cube  and  octahedron. 

OTHER  CLASSES  IN  THE  ISOMETRIC  SYSTEM. 

28.  CLASS  OF  THE  TETARTOID. — Three  axes  of  two-fold  sym- 
metry at  90°  to  cube  faces  and  four  of  three -fold  through  opposite 
corners  of  the  cube.      Example  —  Ullmannite. 

29.  CLASS  OF  THE  GYROID.  —  Three  axes  of  four-fold  symmetry, 
at  90°  to  cube  faces,  four  of  three-fold  through  opposite  corners  of 
cube,  six  of  two-fold    through  diagonally  opposite  edges.      Ex- 
amples —  Sylvite,    sa-lammoniac. 


CHAPTER   VIII. 


TWIN  CRYSTALS  OR  MACLES. 

CRYSTALS  frequently  form  which  evidently  consist  of  two  indi- 
viduals one  of  which  is  reversed  with  respect  to  the  other.  In  such 
crystals  reentrant  angles  are  common  and  familiar  shapes  are  fre- 
quently suggested  such  as  crosses,  Fig.  188,  hearts,  Fig.  189,  and 
arrow-heads,  Fig.  190. 


FIG.  1 88. 


FIG.  190. 


Such  growths  are  called  twin  crystals  or  macles.  When  two 
individuals  penetrate  each  other  they  constitute  a  penetration  twin, 
and  when  they  do  not  they  constitute  a  contact  or  juxtaposition  twin, 
the  distinction  between  these  being  unimportant. 

With  respect  to  their  symmetry  twin  crystals  may  be  divided  into : 


FIG.  191. 


FIG.  192. 


FIG.  193. 


(a)  Reflection  Twins.  —  Symmetrical  to  a  so-called  "  twin  plane" 
which  is  always  parallel  to  a  possible  face  of  the  crystal  but  being 

61 


62 


CR  YSTALLOGRAPHY. 


a  plane  of  symmetry  for  the  pair  of  crystals,  cannot  be  a  plane  of 
symmetry  for  either  individually.  Fig.  191  shows  a  gypsum 
crystal  with  a  shaded  plane  parallel  to  the  orthopinacoid,  and  Fig. 
192  shows  the  corresponding  reflection  twin. 

(b)  Rotation  Twins.  —  Symmetrical  to  a  so-called  "  Twin  Axis  " 
which  is  always  parallel  to  a  possible  edge  of  the  crystal  but 
cannot  be  an  axis  of  two-fold,  four-fold,  or  six-fold  symmetry, 
because  a  rotation  of  180°  about  it  would  bring  the  crystals  into 
an  identical  instead  of  a  reversed  position. 

Fig.  193  shows  an  interpenetrating  rotation  twin  of  orthoclase, 
the  twin  axis  being  parallel  an  edge  of  the  prism. 
Repeated  Twinning.     (Polysynthetic  Twins,  Pscudo  Symmetry?) 

Frequently  there  is  a  repetition  of  the  twinning,  a  third  individual 
occurring  reversed  upon  the  second,  a  fourth  upon  the  third  and 
so  on. 

FIG.  194.  FIG.  195. 


If  the  successive  twin  planes  are  parallel  the  phenomenon  is 
called  polysynthetic  twinning  and  there  often  result  crystals  in 
which  the  individuals  have  been  reduced  to  thin  lamellae  and  the 


FIG.  196. 


FIG.  197. 


FIG.   198. 


reentrant  angles  to  striae.     Fig.  194  shows  an  albite  twin  and  Fig. 
195  repeated  or  polysynthetic  twinning  of  the  same  mineral. 


TWIN  CRYSTALS   OR  MACLES.  63 

If  the  successive  twin  planes  are  oblique  to  each  other  the  regular 
repetition  may  lead  to  what  are  known  as  "  circular  forms." 

For  instance  repeated  twins  of  the  orthorhombic  marcasite  with 
the  prism  face  as  the  twin  plane,  lead  to  a  circular  form  of  five 
individuals,  Fig.  196,  because  the  prism  angle  74°  55'  is  approxi- 
mately 360°  -=-5. 

Sometimes  the  "  circular  form"  approximates  a  shape  belong- 
ing to  a  higher  class  of  symmetry,  for  instance  the  orthorhombic 
aragonite  often  occurs  in  pseudohexagonal  forms,  Fig.  197,  due  to 
twinning  with  the  twin  plane  the  prism  face.  As  the  prism  angle 
is  63°  48'  the  cross  section  is  not  a  perfect  hexagon  as  is  shown, 
Fig.  198. 

Secondary  Twinning. 

Twin  lamellae  may  be  produced  artificially  by  pressure  in  a  num- 
ber of  species,  the  most  familiar  being  that  shown  in  Fig.  277. 
There  are  often  found  in  nature  twin  lamellae  apparently  due  to 
pressure. 

TRICLINIC  TWINS. 

Reflection  Twins.  —  The  brachy  pinacoid  is  the  most  frequent 
twin  plane.  Fig.  1 99  shows  a  twin  of  albite. 

FIG.  199.  FIG.  200. 


Rotation  Twins.  —  In  the  so-called  pericline  twin  of  albite  the 
macro  axis  is  the  twin  axis,  Fig.  200. 

MONOCLINIC  TWINS. 

Rotation  Twins.  —  In  this  system  twins  with  a  twin  axis  parallel 
to  a  prism  edge  are  common. 

Figs.  20 1  and  202  show  such  twins  in  gypsum  and  pyroxene 
and  Fig.  193  shows  a  similar  but  interpenetrating  jtwin  of  ortho- 
clase. 


64 


CR  YSTALLOGRAPHY. 


Reflection  Twins.  —  These  also  occur,  as  for  instance  in  ortho- 
clase,  Fig.  203.     Here  again  the  angle  is  nearly  an  aliquot  part 


FIG.  201. 


FIG.  202. 


FIG.  203. 


of  360,  the  twin  plane  being  parallel  to  the  face  of  a  dome  of  89° 

53'- 

ORTHORHOMBIC  TWINS. 

Reflection  Twins.  —  The  usual  twin  planes  are  faces  of  prisms  or 
domes  and  especially  those  with  angles  near  an  aliquot  part  of  360° 
as  60°  or  72°  or  45°  or  90°. 


FIG.  204. 


FIG.  205. 


FIG.  206. 


Two  such  have  already  been  referred  to  Figs.  196  and  197. 
Fig.  204  shows  the  aragonite  twin,  the  prism  angle  being  63° 
48',  and  Fig.  205  shows  a  twin  of  staurolite,  the  twin  plane  a  brachy 
dome  face  with  angle  of  91°  22',  and  Fig.  206  shows  a  twin  of 
arsenopyrite,  the  twin  plane  a  macro  dome  face  with  an  angle  of 
59°  22'. 

TETRAGONAL   TWINS. 

Reflection  Twins  with  the  twin  plane  a  face  of  the  second  order 
pyramid  are  most  common.  Fig.  207  shows  a  contact  twin  of 
cassiterite  and  Fig.  208  a  contact  twin  of  hausmannite. 


TWIN  CRYSTALS   OR  MACLES. 


Rotation  Twins.  —  In  scheelite,  Fig.  209,  the  twin  axis  is  parallel 
to  a  prism  edge. 


FIG.  207. 


FIG.  208. 


FIG.  209. 


HEXAGONAL   TWINS. 


Twins  are  rare  in  the  class  of  highest  symmetry  of  this  system. 
In  the  scalenohedral  class  twins  occur  with  the  twinning  plane 
parallel  to  a  rhombohedron  or  base  but  not  to  a  prism  face. 


FIG.  210. 


FIG.  211. 


Reflection  Twins  of  calcite  are  shown  in  Fig.  210  which  repre- 
sents the  unit  rhombohedron  with  the  twin  plane  a  :  co  a  :  a  :  \c  ; 
{ioT2}. 

Fig.  2 1 1  shows  a  scalenohedron  twin  with  the  twin  plane  the 
basal  pinacoid. 

Rotation  Twins.  —  Fig.  2 1 1  may  also  be  regarded  as  a  rotation 
twin,  the  twin  axis  parallel  to  a  prism  edge. 

In   quartz,   twins   of  this  kind  occur  like  Fig.   212,  but  more 
frequently  interpenetrating  and  as  then  the  positive  rhombohedron 
of  one  coincides  with  the  negative  of  the  other,  the  twin  structure 
is  only  recognized  by  etching. 
5 


66  CR  YSTALLOGRAPHY. 

Fig.  2 1 3  is  frequently  found  in  quartz  but  is  not  a  true  twin  be- 
FIG.  212.  FIG.  213. 


cause  the  individuals  are  one  positive  and  the  other  negative.    Basal 
sections  will  show  characteristic  optical  phenomena. 


FIG.  214. 


FIG.  215. 


FIG.  216. 


FIG.  217. 


Isometric  Twins. 

Reflection  twins  are  common,  especially  with  an  octahedron  face 
as  the  twin  plane.  Fig.  2 1 4  shows  a  contact 
twin  octahedron  very  frequent  in  the  spinel 
group,  and  2 1  5  the  corresponding  interpene- 
tration  twin,  the  faces  of  one  individual 
shaded.  Fig.  216  shows  the  contact  twin 
cube. 

Rotation  twins  occur,  especially  rotation 
about  a  vertical  edge  (cube  edge).  Fig.  217. 
shows  the  "  Iron  Cross  "  of  pyrite  which  is 

the  twin  pyritohedron  of  this  type.     The  faces  of  one  individual 

are  shaded. 


CHAPTER   IX. 

CRYSTAL  DRAWING  AND  GRAPHIC   SOLUTION  OF  STERE- 
OGRAPHIC    PROJECTIONS. 

FOR  description  and  illustration  crystals  are  usually  projected 
upon  a  vertical  plane  by  parallel  rays  oblique  to  the  plane  of  pro- 
jection. The  eye  is  conceived  to  be  at  an  infinite  distance  but  a 
little  to  the  right  and  above  the  center  of  the  crystal. 

The  figures  obtained  in  this  way 

have  an  appearance  of  solidity,  all  FlG-  2l8- 

parallel  edges  are  parallel  in  the 
projection  and  all  points  in  a  given 
line  remain  the  same ' propo rtionate 
distances  apart. 
Construction  of  "  Axial  Cross." 

A  definite  relation  exists*    be-     — 

tween  the   projected    lengths  and  A  ' 

angles  of  the  isometric  axes  and 
the  angles  of  elevation  and  rota- 
tion to  the  right,  of  the  line  of 
sight. 

For  the  drawings  of  this  book 

the  projected  isometric  "  axial  cross  "  consists  of  three  lines,  Fig. 
218,  intersecting  at  a  common  center  and  with  BOC=g^°  8/» 
AOC=  116°  17'  and  OA  :  OB  :  OC=  37  :  100  :  104. 

Tetragonal  Axial  Cross. 

OA  and  OB  of  the  isometric  cross,  Fig.  218,  are  unchanged 
but  OC  is  multiplied  by  the  value  c  for  the  particular  crystal. 
Thus  if  c  =  0.64  the  half  vertical  axis  is  sixty-four  one-hundredths 
of  the  length  of  OC. 

Orthorhombic  Axial  Cross. 

OB  of  the  isometric  "cross"  is  unchanged;  OA  is  multiplied 
by  the  value  of  a,  and  OC  by  the  value  of  c.  Thus  if  a  :  T> :  c  = 

*  Moses,  Characters  of  Crystals,  p.  79,  for  other  projections. 
67 


68 


CR  YSTALL  OGRAPHY. 


0.815  :  i  :  1.312  OB  is  unchanged,  OA  is  made  approximately 
eight  tenths  of  its  isometric  length  and  OCis  made  approximately 
one  and  one  third  times  its  isometric  length. 

Monoclinic  Axial  Cross. 

One  axis  has  a  different  inclination  to  the  corresponding  isometric 
axis.  To  obtain  this  direction  in  perspective  proceed  as  follows  : 

Upon  the  isometric  "  cross  "  lay  off  Or  =  OC  cos  ,3  and  On  = 
OA  sin  /3,  Fig.  219.  Complete  the  parallelogram  OrDn\  then  is 
DD  the  projection  of  a  line  equal  in  length  to  an  isometric  axis  but 
in  the  direction  of  the  desired  clino  axis. 

OD  is  then  multiplied  by  the  value  of  a  and  OC  by  the  value 
of  c  as  in  the  orthorhombic. 


FIG.  219. 


FIG.  220. 


Triclinic  Axial  Cross. 

The  same  method  is  carried  further,  for  instance,  Fig.  220  :  The 
constants  for  axinite  are  d  :b:c  =  0.492  :  i  :  0.479,  a  A  c  =  ft  = 
91°  52',  b  A^=«=82°  54',  rfA^  =  r  =  131°  39'. 

Vertical  Axis. —  Make  Oc  =  OCX  .479. 

Macro  Axis.  —  Make  Oe  =  OB  sin  131°  39',  and  Od  =  OA  cos 
131°  39';  complete  the  parallelogram  dOcn.  Make  Or  =  On  sin 
82°  54'  and  Ox=  OC  cos  82°  54';  complete  the  parallelogram 
rOxb.  Then  is  Ob  the  projection  of  one  half  the  desired  axis. 

Brachy  Axis.  —  Make  01  =  OC  cos  91  °  52',  and  Op  =  OA  sin 
91°   52'.     Complete  the  parallelogram  /(9/V;  make  (9*2  =  0.492 
X  Ot ;  then  is  Oa  the  projection  of  one  half  the  desired  axis. 
Hexagonal  Axial  Cross. 

The  proportionate  value  of  c  is  laid  off  on  CC'  and  the  basal 
axes  are  derived  as  follows,  Fig.  221  : 


CRYSTAL   DRAWING. 


69 


Make  Op  =  OA  x  1.732  ;  draw  pB  and  /,#';  bisect  <9/  by  a 
line  parallel  to  BB'\  then  are  OB,  Oa  and  Oa3  the  projections  of 
desired  semi-axes. 

Determination  of  the  Direction  of  Edges. 

The  unit  form  is  obtained  by  joining  the  extremities  of  the  axial 
cross  by  straight  lines,  and  other  simple  forms  are  easily  drawn  by 
methods  which  suggest  themselves  ;  FI(J  Mi 

for  instance,  the  unit  prism  by  lines 
through  the  terminations  of  the  basal 
axes  parallel  to  the  vertical  axis.  It 
is  always  possible,  also,  to  obtain 
two  points  of  any  edge  by  actually 
constructing  the  two  planes  and  rind- 
ing the  intersection  of  their  traces  in 
two  axial  planes.  The  method,  how- 
ever, is  cumbersome. 

In  all  systems  the  projected  inter- 
sections of  any  planes  may  be  simply  tf 
found  by  the  following  method  : 

(a)  Draw  the  axial  cross  as  previously  directed. 

(b]  Reduce  each  symbol  of  Weiss  by  dividing  all  coefficients  by 
the  coefficient  of  c. 


FIG.  222. 


Or  reduce  each  symbol  of  Miller  by  taking  the  reciprocals  and 
dividing  each  term  therein  by  the  third. 

(r)  The  symbols  now  represent  each  face  moved  parallel  to 
itself  until  it  cuts  c  at  a  unit's  length. 

Therefore  any  edge  has  one  point  at  c  and  another  at  the  inter- 


CR  YSTALLOGRAPHY. 


FIG.  223. 


section  of  the  traces  of  the  two  faces  on  the  plane  of  the  basal 
axes. 

The  method  will  be  sufficiently  illustrated  by  following  in  detail 
the  construction  for  the  intersections  of  /,  y  and  /  of  the  topaz 
crystal,  Fig.  223. 

In  Fig.  222,  AA,  BB  and  CC  form  the  projected  axial  cross  of 
topaz. 

The  faces  /,  y  and  p  are  respectively  20.  :  b  :  co  c,  oo  a  :  b  :  4*7 
and  a  :  b  :  c.  If  these  are  moved  each  parallel  to  itself  until  they 
intersect  c  at  unity  their  symbols  (dividing  by  the  coefficients  of  c 
in  each  case)  will  be  oa  :  ob  :  c,  coa  :  ^b  :  c,  a  :  b  :  c. 

The  Miller  Indices  are  120,  041,  ill,  their  reciprocals  are  l^co,  co^i,  m,  and 
these,  each  divided  by  the  third,  reduce  to  ooi,  oo^l,  in,  which  are  identical  with  the 
coefficients  already  obtained. 

Their  traces  upon  the  plane  AOB,  Fig.  222,  will  be  therefore 
respectively  : 

For  /,  the  line  LL  through  the  cen- 
ter but  parallel  to  its  former  position 
at  which  it  cuts  at  20,  and  b. 

For  jf,  the  line  YY  parallel  A  A  and 
intersecting  at  one  fourth  b. 

For  p  the  line  AB  intersecting  the 
axes  at  a  and  b. 

The  lines  LL  and  YY  intersect  at 
vS ;  therefore  SC  is  the  direction  of  in- 
tersection of  /  and  y. 

The  lines  LL  and  AB  intersect  at 
L ;  therefore  LC  is  the  direction  of  intersection  of /and/. 

All  other  intersections  may  be  obtained  in  the  same  manner  on 
any  axial  cross. 
Construction  of  the  Figure. 

The  edge  directions  thus  found  are  now  to  be  united  in  ideal 
symmetry,  yet  so  as  to  show,  as  far  as  possible,  the  relative  de- 
velopment of  the  forms. 

A  second  axial  cross  is  drawn  parallel  to  that  used  in  determin- 
ing the  edge  directions  and  these  are  transferred  by  triangles,  care 
being  taken  that  all  corresponding  dimensions  are  in  their  proper 
proportions  and  in  accord  with  the  planes  of  symmetry.  Gen- 
erally it  will  be  best  to  pencil  in  and  verify  the  principal  forms  and 
later,  to  work  in  the  minor  modifying  planes. 


CRYSTAL   DRAWING. 


The  back  (or  dotted)  half  of  most  crystals  can  be  obtained  by 
marking  the  angles  of  the  front  half  on  tracing  paper,  turning  the 
paper  in  its  own  plane  1 80°  and  pricking  through.  This  is  also  a 
test  of  accuracy,  for  the  outer  edges,  angle  for  angle,  should  coincide. 


GRAPHIC  DETERMINATION  OF  INDICES  AND  AXIAL 
ELEMENTS. 

The  stereographic  projection  having  been  made  as  described, 
page  14,  the  position  of  the  faces  001,010,  100  (pinacoids)  being 
known  and  a  plane  having  been  chosen  as  1 1 1  or  two  planes  as 
two  of  no,  101  and  on  ;  it  is  possible  to  determine  graphically 
the  axial  elements  and  the  indices  of  all  other  occurring  faces  with 
sufficient  accuracy  to  ascertain  the  true  rational  indices. 

A.     SIMPLE  DEVICE  FOR  THE  DETERMINATION  OF  INDICES  BY  ZONE 
RELATIONS. 

A  zone  is  a  series  of  faces  which  intersect  in  parallel  edges.  In 
the  projection  all  poles  of  a  zone  are  projected  in  the  same  great 
circle  and  it  is  assumed  that  all  prominent  zones  through  the  ooi, 
oio  or  loo  poles  have  been  drawn. 

If  two  of  the  indices  of  any  face  of  a  zone  are  zero,  the  ratio  of 
the  corresponding  indices  is  constant  for  all  faces  of  the  zone.  Hence : 

For  a  zone  through  ooi  or  00(0)  i,  kjk  is  constant  for  all  faces. 
For  a  zone  through  100  or  io(T)o,  kjl  is  constant  for  all  faces. 
For  a  zone  through  oio  or  oi(T)o,  hjl  is  constant  for  all  faces. 

The  indices  of  a  face  at  the  FIG.  224. 

intersection  of  two  such  zones 
will  result  if  in  each  zone  a  sec- 
ond face  is  known.  The  desired 
values  may  be  obtained  by  writ- 
ing the  indices  of  the  two  known 
faces,  omitting  the  term  in  each 
not  part  of  the  constant  ratio, 
and  then  multiplying  the  cor- 
responding pair  for  one  index 
and  diagonal  pairs  for  the  other 
two  indices. 

EXAMPLE.  —  In  Fig.  224  let  the  pinacoids  and  (in),  (310), 
(305),  and  (130),  be  known,  to  find  the  indices  of  planes  projected 


oio 


CR  YSTALLOGRAPHY. 


at  a,  b,  c,  d,  e,  f,  g,  h,  i,  k.  All  calculations  are  either  like  //  in 
zones  [oio  305]  and  [100  in],  or  like  i  in  zones  [ooi  130]  and 
[100  in]. 


3  —  5 


^=(355) 


'•=(133) 


i     3     3 


Similarly  «  =  (3 1 5),  £=(335),  r=  (395),  d=  (313),  ^  =  (131), 


In  the  hexagonal  system  the  third  index  is  omitted. 

EXAMPLE. — hkll\\&s  in  the  zone  1010  :  0221  and  also  in  the  zone 
Olio  :  1 121.  Omitting  I  and  writing  the  constant  ratios  as  before, 
there  result 

— 2     i 


hkl=  121 


hkll=  1231. 


B.     GRAPmC  DETERMINATION  BY  {hko}-,  {okl}-,  AND  {hoi;    FACES. 
For  faces  (hkl)  the  corresponding  faces  (hko\  (okl}  and  (hoi]  are 
found  by  the  zone  circles  through  (ooi),  (100)  and  (oio)  (Fig.  225). 


FIG.  226. 


In  the  hexagonal  system  the  {hkll}  faces  are  found  similarly  by 
the  zone  circles  through  (oooi),  (1010)  and  (oiTo)  (Fig.  226) 
and  determining  the  corresponding  (Iikio),  (ohhl]  and  (ho/il)  faces. 
It  is  then  possible  to  read  directly  the  ratios  hjk,  kfl  and  hjl,  on  a 
scale,  the  position  of  which  can  be  found  by  a  simple  construction. 


CRYSTAL   DRAWING. 


Graphic  Determination  of  hjk. 

In  any  system  with  axes  at  right  angles  (isometric,  tetragonal 
or  orthorhombic)  the  ratio  of  hjk  can  be  graphically  determined 
on  the  stereographic  projection.  For  instance  in  Fig.  225  to  find 
the  ratio  of  hjk. 

Find  T,  Fig.  227,  the  intersection  of  the  radius  through  1 10  and 


FIG.  228. 


R' 


the  tangent  at  A.  Take  RT  parallel  to  CA  as  equal  I  (unity). 
Then  the  radius  through  any  other  pole  as  hkl  will  cut  this  line  RT 
at  a  point  T1  such  that  RT1 '=  h\k. 

In  the  drawing  hjk  =  1.5. 

In  the  hexagonal  system  similarly  find  T,  the  common  intersec- 
tion, Fig.  228,  of  the  radius  through  1120  and  the  lines  RT  and 
R' T  parallel  respectively  to  CR'  and  CR. 

Take  RT  =  R'Tas  unity.  Then  the  prolongation  of  the  radius 
through  any  pole,  hkil,  cuts  these  lines  in  points  T'  (on  RT  not 
shown)  and  T"  such  that 


RT' 


first  index 
second  index ' 


second  index 

R  T    =  -  ^ — — — — j • 

first  index 


For  the  monoclinic  and  triclinic  systems  the  constructions  are  a 
little  more  complex.* 

*See  School  of  Mines  Quarterly,  Vol.  24,  pp.  1 8  and  20. 


74 


CR  YSTALLOGRAPHY. 


Graphic  Determination  of  /£//. 

For  all  isometric,  tetragonal,  orthorhombic  or  hexagonal  crystals 
kjl  may  be  determined  graphically  from  the  stereographic  projec- 
tion as  follows  :  In  the  fourth  quadrant  of  the  projection  lay  off  />  * 
of  01 1  (01 1 1  in  hexagonal)  from  A' ,  Fig.  229,  and  find  T  the  inter- 
section of  the  corresponding  radius  with  the  tangent  at  B.  Take 
RT  parallel  CB  as  unity.  Lay  off  from  A'  the  angle  />  of  any 
okl  face  (in  hexagonal  any  ohhl  face)  and  find  the  intersection  T' 
of  the  corresponding  radius  with  RT.  Then  is  RT'  =  kjl. 

FIG.  229. 


In  the  drawing  kjl=  1.5.  If  the  determination  of  hfk  given 
above  relates  to  the  same  face  then  h  :  k  :  I  =  1.5:1:1/1. 5  or 
9:6:4  that  is  hkl  =  964. 

Graphic  Determination  of  Elements. 

Tetragonal  c  =  A' T",  Fig.  229. 
Hexagonal  c  =  A'T"  x  0.866,  Fig.  229. 
Orthorhombic  c  =  A'T",  Fig.  229. 
a  =  AT,  Fig.  227. 

*  See  pages  6  and  14  for  p. 


PART    II. 


BLOWPIPE  ANALYSIS. 


CHAPTER   X. 

APPARATUS,  BLAST,  FLAME,  ETC. 
The  Blowpipe. 

FIG.  230. 

The  best  form   of  blowpipe  (Fig.  230)  consists 
of: 

1.  A   tapering  tube  of  brass  or  German  silver 
(.5),  of  a  length  proportionate  to  the  eyesight  of 
the  user. 

2.  A  horn  or  hard  rubber    mouthpiece   (£7)  at 
the  larger  end  of  the  tube.      This   should   be   of 
trumpet-shape  to  fit  against  the  lips. 

3.  A  moisture  chamber  (A)  at  the  smaller  end 
of  the  tube  connected  by  ground  joints  to  : 

4.  A    tapering    jet   (ft)   at    right  angles    to  the 
moisture  chamber. 

5.  A  tip  of  platinum  or  brass  (c),  shown  enlarged, 
which   should  be    bored   from   a  solid   piece,    and 

with  an  orifice  of  o.  5  millimeter  diameter. 
The  tip  is  by  far  the  most  important  part 
of  the  blowpipe,  and,  if  correctly  made, 
the  flame  produced  will  be  perfectly  reg- 
ular and  will  not  flutter. 

When  not  in  use  the  blowpipe  should 
be  so  placed  that  the  tip  is  supported 
free  from  contact.  If  the  tip  is  clogged 
by  smoke  or  otherwise  it  should  be 

burned  out  or  cleaned  with  the  greatest  care  so  as  not  to  injure 

the  regular  form  of  the  orifice. 

75 


BLOWPIPE  ANALYSIS. 


Gas  Blowpipe. 

For  most  purposes  the  gas  blowpipe,  Fig.  231,  is  a  convenient 
form  and  is  extensively  used.  The  flame  is  not  quite  so  hot  as 
that  from  rape-seed  oil,  but  is  sufficient  to  round  the  edges  of  a 
calamine  splinter.  Oxidation  and  reduction  are  easily  obtained 
and  the  cleanliness  and  ease  of  control  cause  it  to  be  preferred  by 

FIG.  231. 


many.     The  ordinary  blowpipe  can  be  made  into  a  gas  blowpipe 
by  means  of  an  attachment  to  connect  to  the  moisture  chamber. 

Blowpipe  Lamps. 

Bunsen  Burner.  —  The  simplest  form  of  lamp  for  laboratory  pur- 
FIG.  232.  FIG.  233. 


poses  is  the  ordinary  Bunsen  burner,  Fig.  232,  using  gas  and  fur- 
nished with  a  special  top  (a),  or  an  inner  tube  shaped  to  spread 


APPARATUS,    BLAST,    FLAME.  77 

the  flame.  When  used  with  the  blowpipe  the  orifices  (ft)  at  the 
bottom  of  the  burner  should  be  closed,  so  that  no  air  enters  with 
the  gas.  A  flame  about  4  cm.  high  gives  the  best  results. 

The  hottest  flame  and  greatest  variations  in  quantity  and  quality 
of  flame  are  obtained  from  oils  rich  in  carbon,  such  as  refined  rape- 
seed,  or  olive  or  lard  oil,  or  from  mixtures  of  turpentine  and  alco- 
hol. These  can  be  used  in  the  field  and  where  gas  is  not  available. 
In  some  kinds  of  blowpipe  work  they  are  to  be  preferred  to  gas, 
but  will  not  serve  for  bending  glass  or  for  heating  without  the 
blowpipe. 

Berzdius  Lamp.  —  A  lamp  with  two  openings,  Fig  233,  is  gen- 
erally used  for  oil. 

The  wick  should  be  soft,  close-woven  and  cylindrical,  such  as 
is  used  with  Argand  lamps.  It  should  be  folded  and  inserted  with 
the  opening  toward  the  lower  side  of  the  brass  holder. 

To  fill  the  lamp  both  caps  are  removed  and  the  oil  poured  in 
through  the  smaller  orifice.  During  work,  the  smaller  cap  is  hung 
on  the  vertical  rod ;  the  larger  is  placed  over  the  smaller  orifice 
loosely,  keeping  out  the  dust,  but  admitting  the  needed  air. 

The  lamp  is  lighted  by  blowing  a 
flame  up  and  across  the  wick.  When  FlG- 

well    charred,    the    wick    is    carefully 
trimmed  parallel  to  the  brass  holder. 

Fletcher  Lamp.  —  The  Fletcher  blow- 
pipe lamp,  Fig.  234,  gives  good  satisfac- 
tion, and  a  modified  form,  burning  solid 
fats,  tallow  or  paraffine,  is  especially 
adapted  for  field  work. 

Supports  of  Charcoal,  Plaster,  Etc. 

Charcoal.  —  Charcoal  made  from  soft  woods,  such  as  willow  or 
pine,  is  used  to  support  the  substance  and  receive  any  coats  or 
sublimates  that  may  form,  and,  in  a  measure,  is  a  reducing  agent. 
A  convenient  size  is  4  inches  long,  i  inch  broad,  and  ^  inch  thick. 

Plaster.  —  Plaster  tablets  are  used  for  the  same  purpose.  These 
are  prepared  by  making  a  paste  of  plaster  of  Paris  and  water,  just 
thick  enough  to  run,  which  is  spread  out  upon  a  sheet  of  oiled 
glass  and  smoothed  to  a  uniform  thickness  (j^"  to  %")  by  another 
smaller  sheet  of  glass,  which  may  be  conveniently  handled  by  gum- 
ming a  large  cork  to  one  side  and  using  it  as  a  plasterer's  trowel. 


78  BLOWPIPE  ANALYSIS. 

While  still  soft,  the  paste  is  cut  with  a  knife  into  uniform  slabs, 
4"  by  \y2".  It  is  then  dried,  after  which  the  tablets  are  easily 
detached. 

Aluminum  and  Glass.  —  Ross  used  supports  of  aluminum  plate 
and  Goldschmidt  has  recommended  catching  the  sublimates  on 
glass  plates  upon  which  they  can  be  microscopically  examined 
or  submitted  to  wet  treatment. 

Miscellaneous  Apparatus : 

Each  student  should  have  at  his  desk,  in  addition  to  blowpipe, 
blowpipe-lamp,  charcoal  and  plaster  : 

FORCEPS,  with  platinum  tips  for  fusion  tests.     The  most  con- 

FIG.  235. 


venient  form  is  shown,  Fig.   235,  the  platinum  ends  projecting  at 
least  three  fourths  of  an  inch. 

PLATINUM  WIRE  AND  HOLDER.  — Wire  of  the  thickness  of  about 
one  half  millimeter.     The  handle  for  holding  this  is  sometimes 
only  a  short  piece  of  small  glass  tubing,  into  the  end  of  which  the 
FIG.  236.      w^re  is   fused.     A  holder  in  which  the  wires  can  be 
changed  and  with  a  receptacle  for  a  stock  of  wires,  is 
more  convenient. 

REAGENT  BOTTLES.  —  Four  2-oz.  wide-mouthed 
bottles  ;  for  borax,  soda,  salt  of  phosphorus,  and  bis- 
muth flux  will  be  needed  at  all  times.  It  is  better  to 
have  at  least  eight  such  bottles  in  a  convenient  stand. 
ANVIL.  —  Slab  of  polished  steel,  about  i  \"  by  I  \" 
by  \". 

HAMMER.  —  Steel,  with  square  face,  f  "  or  \" .     As 
in  Fig.  236. 

CLOSED  AND  OPEN  TUBES. 

CUPEL    HOLDER  AND   CUPELS,   for  silver  determi- 
nation. 

Other  important  pieces  of  apparatus  are  :  bar  magnet,  with 
chisel  edge  ;  trays,  for  dirt  and  for  charcoal ;  lens,  knife,  and  watch 
glasses  ;  blue  and  green  glasses  ;  steel  forceps  and  lamp  scissors 
for  trimming  wick  ;  cutting  pliers,  for  cutting  bits  from  minerals  to 


APPARATUS,    BLAST,    FLAME.  79 

be  tested  ;  agate  mortar  and  pestle,  which  can  be  obtained  I  \"  in 
diameter ;  small  porcelain  dishes,  ivory  spoon  and  dropping  tube. 


BLAST   AND   FLAME. 

The  Blast. 

The  blast  is  produced  by  the  muscles  of  the  distended  cheeks, 
and  not  by  the  lungs. 

It  is  best  to  sit  erect,  with  the  blowpipe  held  lightly  but  firmly 
in  the  right  hand,  and  with  the  elbows  against  the  sides.  Then, 
with  the  cheeks  distended  and  the  mouth  closed,  place  the  mouth- 
piece against  the  lips,  breathe  regularly  through  the  nose,  and 
allow  air  to  pass  into  the  pipe  through  the  lips.  From  time  to 
time,  as  needed,  admit  air  to  the  mouth  from  the  throat.  In  this 
manner,  after  learning  to  breathe  through  the  nose  while  keeping 
the  cheeks  distended,  a  continuous  blast  can  be  blown  without 
fatigue. 

The  Flame. 

A  LUMINOUS  FLAME  (Fig.  237)  usually  shows  three  distinct  por- 
tions. 

1.  A  very  hot  non-luminous  veil,  a,  of  carbon 
dioxide  and  free  oxygen. 

2.  A  yellow    luminous    mantle,    b,    of  burning 
gases  and  incandescent  carbon. 

3.  An  interior  dark  cone,  c,  of  unburned  gases, 
not  always  visible. 

Oxidation  and  Oxidizing  Flame. 

The  oxidizing  flame  is  non-luminous,  for  lumi- 
nosity indicates  unconsumed  carbon,  and  hence  a 
reducing  action. 

To  produce  such  a  flame,  place  the  tip  of  the 
blowpipe  almost  touching  the  top  of  the  burner, 
or  the  wick,  and  extending  in  ^  the  breadth 
of  the  flame ;  blow  parallel  to  the  burner  top  or  wick  until  there 
is  produced  a  clear  blue  flame  nearly  an  inch  long.  This  blue 
flame  is  weakly  reducing,  but  just  beyond  the  blue  at  a  (Fig.  238)  is 
an  intensely  hot,  nearly  colorless  zone,  which  is  strongly  oxidizing, 
and  the  bead  is  held  in  this  usually  as  far  from  the  tip  of  the  blue 
flame  as  the  bead  can  be  kept  fluid.  If  the  substance  to  be  oxi- 
dized is  supported  on  charcoal,  a  weak  blast  must  be  used. 


8o 


BLOWPIPE   ANALYSIS. 


With  the  gas  blowpipe  all  that  is  necessary  is  to  avoid  an  excess 
of  gas.  The  blue  flame  is,  as  before,  surrounded  by  the  oxidizing 
colorless  mantle. 

Testing  Purity  of  Oxidizing  Flame.  —  A  loop,  Fig.  239,  about 
3  mm.  in  diameter,  is  made  in  platinum  wire  by  bending  it  around 

FIG.  238.  FIG.  239. 


a  pencil  point,  or  with  the  forceps,  so  that  the  end  meets  but  does 
not  cross  the  straight  part.  This  loop  is  heated  and  dipped  into 
the  flux,  and  the  portion  of  flux  that  adheres  is  fused  to  a  clear 
bead,  more  being  added  until  the  bead  is  of  good  full  shape.* 

Molybdic  oxide,  MoO3,  is  then  dissolved  in  the  bead  at  the  tip 
of  the  blue  flame,  giving  a  brown  to  black  bead  from  production 
of  MoO2  but,  if  moved  to  a,  Fig.  238,  the  color  is  readily  removed 
by  the  reoxidation  of  the  MoO2  and  the  bead  made  colorless. 

FIG.  240. 


Reduction  and  the  Reducing  Flames. 

To  blow  the  yellow  reducing  flame,  Fig.  240,  place  the  tip  of 
the  blowpipe  one  eighth  of  an  inch  above  and  back  of  the  middle 
of  the  flame,  blow  strongly  parallel  to  the  burner  top  or  wick,  and 
turn  the  entire  flame  in  the  direction  of  the  blast. 

*  When  the  flux  is  salt  of  phosphorus,  the  wire  should  be  held  over  the  flame  so  tha/ 
the  ascending  hot  gases  will  help  to  retain  the  flux  upon  the  wire. 


APPARATUS,    BLAST,    FLAME.  8 1 

The  blast  must  be  continuous  ;  too  strong  to  produce  a  sooty 
flame,  and  not  strong  enough  to  oxidize  by  excess  of  air. 

The  blue  flame  also  is  reducing  because  of  the  carbon  monoxide 
it  contains,  but  it  is  not  generally  as  effective. 

With  the  gas  blowpipe  reduction  is  obtained  by  using  a  larger 
flame  and  inserting  the  bead  within  the  blue ;  or  with  large  excess 
of  gas  a  yellow  reducing  flame  may  be  obtained. 

Testing  Purity  of  Reducing  Flame.  —  Manganese  dioxide,  MnO2, 
is  dissolved  in  a  borax  bead  in  the  oxidizing  flame  ;  if  only  a  little 
is  used  the  bead  is  violet  red  when  cold,  and  may  be  made  color- 
less in  the  reducing  flame.  Or  cupric  oxide  or  oxide  of  nickel 
may  be  dissolved  in  a  borax  bead  until  the  bead  is  opaque,  and 
then  reduced  on  charcoal  to  a  clear  bead  and  a  metallic  button. 


CHAPTER   XI. 

OPERATIONS   OF  BLOWPIPE   ANALYSIS. 

Fusion. 

THE  hottest  portion  of  the  flame  is  just  beyond  the  tip  of  the  blue 
flame.  In  some  instances,  noticeably  certain  iron  ores,  substances 
infusible  in  the  oxidizing  flame  are  fusible  in  the  reducing  flame. 

The  test  will  be  differently  made,  according  to  the  material. 

(a)  If  metallic  or  reducible,  treat  in  a  shallow  hole  on  charcoal, 
using  a  fragment  of  the  substance  the  size  of  a  pin's  head. 

(b)  If  stony  or  vitreous,  treat  a  small  sharp-edged  fragment  in 
the  platinum  forceps,  at  the  tip  of  the  blue  flame,  directing  the 
flame  upon  the  point. 

(c)  If  in  powder,  or  with  a  tendency  to  crumble,  grind  and  mix 
with  water  to  fine  paste,  spread  thin  on  coal  and  dry,  and,  if  cohe- 
rent, hold  in  the  forceps.     If  not  coherent  dip  a  moistened  platinum 
wire  in  the  powder,  and  treat  the  adhering  powder  in  the  flame. 

There  will  be  noted  both  the  degree  of  fusibility  and  manner  of 
fusion. 

The  degree  of  fusibility  is  stated  in  much  the  same  way  as  the 
hardness  by  comparing  it  with  a  scale  of  fusibility.  It  is  gener- 
ally, however,  sufficient  to  class  a  mineral  as  simply  easily  fusible, 
fusible,  difficultly  fusible,  or  infusible.  For  purposes  of  compari- 
son, the  following  scale,  suggested  by  v.  Kobell,  is  usually 
adopted : 

1.  Stibnite,  coarse  splinters  fuse  in  a  candle  flame. 

2.  Natrolite,  fine  splinters  fuse  in  a  candle  flame. 

3.  Garnet  (Almandite],  coarse  splinters   easily  fuse  before  the 
blowpipe. 

4.  Actinolite,  coarse  splinters  fuse  less  readily  before  the  blow- 
pipe. 

5.  Orthoclase,  only  fused  in  fine  splinters  or  on  thin  edges  before 
the  blowpipe. 

6.  Calamine,  finest  edge  only  rounded  in  hottest  part  oi  flame. 

7.  Quartz,  infusible,  retaining  the  edge  in  all  its  sharpness. 

82 


.    OPERATIONS    OF  BLOWPIPE  ANALYSIS. 


The  trial  should  always  be  made  on  small  and  fine  pointed  frag- 
ments.    Penfield  recommends  using  a  standard  size  about  I  mm. 
in  diameter  and  4  mm.  long.     The  fragment  should  project  beyond 
the  platinum  as  in  Fig.  241,  so 
that  heat  may  not  be  drawn  off 
by  the  platinum,  and  the  flame 
directed  especially  upon  the  point. 
It  is  always  well  to  examine  the 
splinter  with  a  magnifying  glass, 
before  and  after  heating,  to  aid 
the  eye  in  determining  whether 
the  edges  have  or  have  not  been 
rounded  by  the  heat. 

TJic  manner  of  fusion  may  be 
such  as  to  result  in  a  glass  or  slag 

which  is  clear  and  transparent,  or  white  and  opaque,  or  of  some 
color,  or  filled  with  bubbles.  There  may  be  a  frothing  or  intu- 
mescence, or  a  swelling  and  splitting  (exfoliation).  In  certain 
instances  the  color  and  form  may  change  without  fusion,  etc. 

FLAME  COLORATION. 

During  the  fusion  test  the  non-luminous  veil  is  sometimes  un- 
changed, but  it  is  often  enlarged  and  colored  by  some  volatilizing 
constituent.  There  is  frequently  a  bright  yellow  coloration  due  to 
sodium  salts,  but  this  gives  place  to  the  color  proper. 

The  flame  is  best  seen  in  a  dark  room  or  against  a  black  back- 
ground, such  as  a  piece  of  charcoal,  and  is  often  improved  by 
hydrochloric  acid  and  occasionally  by  other  reagents. 

Some  elements  color  the  flame  best  at  a  gentle  heat,  others  only  at 
the  highest  heat  attainable.  A  good  method  to  cover  all  cases  is  to 
dip  the  end  of  a  flattened  platinum  wire  first  in  hydrochloric  acid  and 
then  in  the  finely  powdered  substance  and  hold  it  first  in  the  mantle 
flame  near  the  wick  and  then  at  the  hottest  portion  at  the  tip  of  the 
blue  flame.  It  is  possible  in  this  way  to  obtain  two  distinct  flames 
such  as  the  red  of  calcium  and  the  blue  from  copper  chloride. 

The  colors  can  also  often  be  seen  to  decided  advantage  by 
simply  holding  the  wire  in  the  non-luminous  flame  of  a  Bunsen 
burner  or  even  in  the  flame  of  an  alcohol  lamp. 

Flame  tests  for  Ca,  Sr  and  Ba  are  not  usually  obtainable  from 
silicates. 


84  BLOWPIPE   ANALYSIS. 

The  important  flame  colorations  are  : 
Yellows. 

YELLOW.  —  Sodium  and  all  its  salts.  Invisible  with  blue  glass. 
Reds. 

CARMINE.  —  Lithium  compounds.  Masked  by  soda  flame. 
Violet  through  blue  glass.  Invisible  through  green  glass. 

SCARLET.  —  Strontium  compounds.  Masked  by  barium  flame. 
Violet  red  through  blue  glass.  Yellowish  through  green  glass. 

YELLOWISH.  —  Calcium  compounds.      Masked  by  barium  flame. 
Greenish  gray  through  blue  glass.      Green  through  green  glass. 
Greens. 

YELLOWISH.  —  Barium  compounds,  molybdenum  sulphide  and 
oxide  ;  borates  especially  with  sulphuric  acid  or  boracic  acid  flux. 

PURE  GREEN.  —  Compounds  of  tellurium  or  thallium. 

EMERALD.  —  Most  copper  compounds  without  hydrochloric  acid. 

BLUISH.  —  Phosphoric  acid  and  phosphates  with  sulphuric  acid. 

FEEBLE. — Antimony  compounds.     Ammonium  compounds. 

WHITISH.  —  Zinc. 
Blues. 

LIGHT.  —  Arsenic,  lead  and  selenium. 

AZURE.  —  Copper  chloride. 

WITH  GREEN,  —  Copper  bromide  and  other  copper  compounds 
with  hydrochloric  acid. 
Violet. 

Potassium  compounds.  Obscured  by  soda  flame.  Purple  red 
through  blue  glass.  Bluish  green  through  green  glass.  In  sili- 
cates improved  by  mixing  the  powdered  substance  with  an  equal 
volume  of  powdered  gypsum. 

USE  OF  THE  SPECTROSCOPE. 

When  salts  of  the  same  metal  are  volatilized  in  the  non-lumi- 
nous flame  of  a  Bunsen  burner  the  spectra  produced,  on  de- 
composing the  resultant  light  by  a  prism,  will  show  lines  identical 
in  color,  number  and  relative  position.  Salts  of  different  metals 
will  yield  different  lines. 

Although,  with  pure  salts,  the  already  described  flame  color- 
ations are  generally  distinct  and  conclusive,  it  will  frequently  hap- 
pen that  in  silicates  or  minerals  containing  two  or  more  reacting 


OPERATIONS   OF  BLOWPIPE  ANALYSIS. 


FIG.  242. 


substances  the  eye  alone  will  fail  to  identify  the  flame  coloration. 
It  is  well  therefore  to  supplement  the  ordinary  flame  tests  by 
spectroscopic  observation.  In  the  blowpipe  laboratory  the  chief 
use  of  the  spectroscope  will  be  to  identify  the  metals  of  the  potas- 
sium and  calcium  families  singly  or 
in  mixtures.  For  this  purpose  the 
direct  vision  spectroscope  of  Hoff- 
man, Fig  242,  is  the  most  con- 
venient. 

The  substance  under  examination 
should  be  moistened  with  hydro- 
chloric acid  and  brought  on  a  plati- 
num wire  into  the  non-luminous 
flame  of  the  Bunsen  burner  as  in  the 
ordinary  flame  test.  In  viewing  the 
flame  through  the  properly  adjusted 

spectroscope  certain  bright  lines  will  be  seen,  and  by  comparing 
these  with  the  chart,  Fig.  245,  or  with  substances  of  known  com- 
position, the  nature  of  the  substance  may  be  determined.  The 
sodium  line  will  almost  invariably  be  present  and  the  position  of 
the  other  lines  will  be  best  fixed  by  their  situation  relative  to  this 
bright  yellow  line. 

The  more  ordinary  form  of  spectroscope,  Fig.  243,  has  special 


FIG.  243. 


advantages  in  allowing  an  easy  comparison  of  flames.  A  is  the 
observation  telescope,  B  the  collimator  through  which  the  light 
from  the  flames  Mand  M'  is  sent  as  parallel  rays  through  the  prism 


86 


BL  O  WPIPE  ANAL  YSIS. 


FIG.  244.  p  to  the  telescope  A.     The  third  telescope 

C  sends  the  image  of  a  micrometer  scale  to 
A  by  which  the  relative  distance  apart  of 
the  lines  is  judged. 

Fig.  244  shows  an  enlarged  view  of  the 
collimator  B.     By  means  of  the  little  rect- 
angular prism  i  the  light  from  a  second  flame 
//,  placed  at  one   side,  is  sent   through  the 
collimator  and  its  spectrum  obtained  side  by  side  with  that  from 

the  flame  G. 

FIG.  245. 


yellow 


violet 


Na 


OPERATIONS   OF  BLOWPIPE  ANALYSIS.  87 

In  this  manner  the  spectrum  of  an  unknown  substance  may  be 

compared  with  that  of  one  of  known   composition   and   if  lines 

of  the  unknown  coincide  with  those  of  the  known  substance  the 

identity  of  at  least  one  of  its  constituents  is  established. 

The  chart  (Fig.  245)  and  brief  description  of  spectra  of  substances 

giving  distinct  lines  with  the  Bunsen  flame  will  be  of  service. 

POTASSIUM  —  two  red  lines  and  one  violet  line. 

SODIUM  —  a  single  bright  yellow  line,  which  with  higher  dispersion 
is  resolved  into  two  lines.  Almost  always  present  from 
the  small  amounts  of  sodium  in  dust. 

LITHIUM  —  one  very  bright  deep  red  line  and  a  faint  line  in  the 
orange. 

STRONTIUM  —  a. number  of  characteristic  red  lines  and  one  blue  line. 

CALCIUM  —  a  bright  red,  and  a  bright  green  line,  with  fainter  red 
to  yellow  lines  and  a  line  in  the  violet. 

BARIUM  —  a  number  of  yellow  and  green  lines. 

RUBIDIUM  —  two  violet  and  two  red  lines  with  several  less  prom- 
inent lines  in  the  orange,  yellow  and  green. 

C/ESIUM  —  two  distinct  blue  lines  and  one  orange  line. 

THALLIUM  —  one  characteristic  green  line. 

INDIUM  —  an  indigo  blue  line  and  a  violet  line. 

VOLATILIZATION. 

In  blowpipe  analysis,  antimony,  arsenic,  cadmium,  zinc,  tin, 
lead,  mercury  and  bismuth  are  always  determined  by  securing 
sublimates  of  either  the  metals  themselves  or  of  some  volatile  oxide, 
iodide,  etc. 

Other  elements  and  compounds,  such  as  sulphur,  selenium,  tel- 
lurium, osmium,  molybdenum,  ammonia,  etc.,  are  also  volatilized 
and  in  part  determined  during  volatilization  as  odors  or  by  sub- 
limates. Certain  other  compounds,  particularly  chlorides  of  sodium 
and  potassium  and  of  some  other  metals,  such  as  copper,  tin  and 
lead,  yield  sublimates  ordinarily  disregarded. 

Volatilization  tests  are  commonly  obtained  on  charcoal,  or 
plaster  or  in  open  and  closed  tubes. 

Treatment  on  Charcoal. 

A  shallow  cavity,  just  sufficient  to  prevent  the  substance  slip- 
ping, is  bored  at  one  end  of  the  charcoal  and  a  small  fragment  or  a 
very  little  of  the  powdered  substance  is  placed  in  it.  The  charcoal 


88  BLOWPIPE  ANALYSIS. 

is  held  in  the  left  hand,  so  that  the  surface  is  at  right  angles  to  the 
lamp  but  tipped  vertically  at  about  120°  to  the  direction  in  which 
the  flame  is  blown. 

A  gentle  oxidizing  flame  is  blown,  the  blue  flame  not  touching 
the  substance,  but  being  just  behind  and  in  a  line  with  it.     After  a 

FIG.  246. 


few  moments  the  test  is  examined  and  all  changes  are  noted,  such 
as  position  and  color  of  sublimates,  color  changes,  odors,  decrepi- 
tation, deflagration,  formation  of  metal  globules  or  magnetic  parti- 
cles. The  heat  is  then  increased  and  continued  as  long  as  the 
same  reactions  occur,  but  if,  for  instance,  a  sublimate  of  new  color 
or  position  is  obtained,  it  is  often  well  to  remove  the  first  sublimate 
either  by  transferring  the  substance  to  another  piece  of  charcoal 
or  by  brushing  away  the  first  formed  sublimate  after  its  satisfac- 
tory identification. 

The  same  steps  should  then  be  followed  using  the  reducing 
flame. 

The  sublimates  differ  in  color  and  position  on  the  charcoal ;  some 
are  easily  removed  by  heating  with  the  oxidizing  flame,  some  by 
the  reducing  flame,  some  are  almost  non-volatile,  and  some  impart 
colors  to  the  flame. 

Treatment  on  Plaster  Tablets. 

Experience  has  shown  that  the  sublimates  obtained  on  charcoal 
and  plaster  supplement  each  other.  The  method  of  using  is  pre- 
cisely the  same  and  white  sublimates  are  easily  examined  by  first 
smoking  the  plaster  surface  by  holding  it  in  the  lamp  flame. 

The  coatings  differ  in  position,  and  to  some  extent  in  color. 


OPERATIONS  OF  BLOWPIPE   ANALYSIS.  89 

Plaster  is  the  hotter  conductor,  condenses  the  oxides  closer  to  the 
assay,  and  therefore,  the  more  volatile  coatings  are  thicker  and 
more  noticeable  on  plaster,  while  the  less  volatile  coatings  are  more 
noticeable  when  spread  out  on  charcoal.  Charcoal  supplements 
the  reducing  action  of  the  flame,  and  therefore  is  the  better  sup- 
port where  strong  reduction  is  desired. 


Comparison  of   Important  Sublimates  on  Charcoal    and    Plaster.* 

I.  Without  Fluxes.  —  Treated  First  in  0.  F.,  then  in  R.  F. 

ARSENIC.  —  White  volatile  coat.  On  smoked  plaster  it  is  crys- 
talline and  prominent ;  on  charcoal  it  is  fainter  and  less  distinct, 
but  the  odor  of  garlic  is  more  marked.  Deposits  at  some  distance 
from  assay.  Fumes  invisible  close  to  assay. 

ANTIMONY. — White  pulverulent  volatile  coat,  more  prominent 
on  charcoal.  Is  deposited  near  assay  and  the  fumes  are  visible 
close  to  assay  after  removal  of  flame. 

SELENIUM. 

On  Charcoal.  —  Horse-radish  odor  and  a  steel-gray  coat. 
On  Plaster.  —  Horse-radish  odor,  brick-red  to  crimson  coat. 

TELLURIUM. 

On  Charcoal. — White  coat  with  red  or  yellow  border. 
On  Plaster. — Deep  brown  coat. 
CADMIUM. 

On  Charcoal. — Brown  coat  surrounded  by  peacock  tarnish. 
On  Plaster. — Dark   brown  coat  shading  to  greenish-yellow 
and  again  to  dark  brown. 

MOLYBDENUM. — Crystalline  yellow  and  white  coat  with  an  outer 
circle  of  ultramarine  blue.  Most  satisfactory  on  plaster. 

LEAD. —       1  Yellow  sublimate  with  outer  fringe  of  white.    More 
BISMUTH. —  /      noticeable  on  charcoal  than  on  plaster. 
ZINC. — White,  not  easily  volatile  coat,  yellow  while  hot.     Best 
on  charcoal. 

TIN. — White  non-volatile  coat  close  to  assay,  yellowish  while 
hot.  Best  on  charcoal. 

*  Certain  compounds  give  a  white  coating  before  the  blowpipe  which  at  times  cause 
confusion.  Among  these  are  many  chlorides  and  the  sulphate  of  lead.  Galena  and 
lead  sulphides  also  give  white  sublimates  which  must  not  be  confused  with  the  arsenic 
or  antimony  coats. 


90  BLOWPIPE  ANALYSIS. 

II.  With  Bismuth  Flux.* 
LEAD. 

On  Plaster. — Chrome  yellow  coat. 

On  Charcoal. — Greenish-yellow,  equally  voluminous  coat. 
BISMUTH. 

On  Plaster. — Chocolate-brown  coat,  with  an  underlying  scar- 
let; with  ammonia  it  becomes  orange-yellow,  and  later  cherry-red. 

On  Charcoal. — Bright  red  band  with  a  fringe  of  yellow. 
MERCURY. 

On  Plaster. — Scarlet  coat  with  yellow,  but  if  quickly  heated  is 
dull  yellow  and  black. 

On  Charcoal. — Faint  yellow  coat. 
ANTIMONY. 

On  Plaster. — Orange  coat  stippled  with  peach-red. 

On  Charcoal. — Faint  yellow  coat. 
ARSENIC. 

On  Plaster. — Yellow  and  orange  coat,  and  not  usually  satis- 
factory. 

On  Charcoal. — Faint  yellow  coat. 
TIN. 

On  Plaster. — Brownish-orange  coat. 

On  Charcoal. — White  coat. 
The  following  tests  show  only  on  the  plaster : 
SELENIUM. — Reddish-brown,  nearly  scarlet. 
TELLURIUM. — Purplish-brown  with  darker  border. 
MOLYBDENUM. — Deep  ultramarine  blue. 

III.  With  Soda  (Sodium  Carbonate  or  Bicarbonate). 
Soda  on  charcoal  exerts  a  reducing  action  partly  by  the  forma- 
tion of  sodium  cyanide,  partly  because  the  salts  sink  into  the  char- 
coal and  yield  gaseous  sodium  and  carbon  monoxide.     The  most 
satisfactory  method  is  to  mix  the  substance  with  three  parts  of  the 
moistened  reagent  and  a  little  borax ;  then  spread  on  the  char- 
coal and  treat  with  a  good  reducing  flame  until  everything  that 
can  be  absorbed  has  disappeared.    Moisten  the  charcoal  with  water, 
break  out  and  grind  the  portion  containing  the  charge.     Wash 
away  the  lighter  part  and  examine  the  residue  for  scales  and 
magnetic  particles. 

*  Two  parts  of  sulphur,  one  part  of  potassium  iodide,  one  part  of  acid  potassium 
sulphate. 


OPERATIONS   OF  BLOWPIPE  ANALYSIS.  91 

The  reduction  may  result  in : 

1 .  Coating,  but  no  reduced  metal. 

Volatile  white  coating  and  garlic  odor,        .         .         .  As. 
Reddish-brown  and  orange  coating  with  characteristic 

variegated  border,         ......  Cd. 

Non-volatile  coating,  yellow  hot  and  white  cold,  .         .  Zn. 

Volatile  steel-gray  coating  and  horseradish  odor,         .  Se, 

Volatile  white  coating  with  reddish  border,         .         .  Te. 

2.  Coating  with  reduced  metal. 

Volatile  thick  white  coating  and  gray  brittle  button,  .  Sb. 
Lemon-yellow  coating  and  reddish-white  brittle  button,  Bi. 
Sulphur-yellow  coating  and  gray  malleable  button,  .  Pb. 
Non-volatile  white  coating,  yellow  hot,  and  malleable 

white  button,        .......     Sn. 

White  coating,  made  blue  by  touch  of  R.  F.,  and  gray 

infusible  particles,         .         .         .         .         .         .     Mo. 

3.  Reduced  metal  only . 

Malleable  buttons,  .....  Cu,  Ag,  Au. 
Gray  magnetic  particles,  ....  Fe,  Co,  Ni. 
Gray  non-magnetic  infusible  particles,  W,  Pt,  Pd,  Ir,  Rh. 

The  carbonate  combines  with  many  substances  forming  both 
fusible  and  infusible  compounds.  Many  silicates  dissolve  with  a 
little  of  the  reagent,  but  with  more  are  infusible  ;  a  few  elements 
form  colored  beads  with  the  reagent,  especially  on  platinum. 

The  residue  left  after  heating  may  contain  malleable  metallic 
beads  of  copper,  lead,  silver,  tin  or  gold.  It  may  consist  of  a 
brittle  easily  fusible  button  of  bismuth,  antimony,  or  the  sulphide, 
arsenide  or  antimonide  of  some  metal.  It  may  be  magnetic  from 
the  presence  of  iron,  cobalt  or  nickel  or  it  may  show  an  alkaline 
reaction,  when  touched  to  moistened  red  litmus  or  tumeric  paper, 
indicating  the  presence  of  some  member  of  the  potassium  or  cal- 
cium group  of  metals. 

Infusible  Compounds.— -Mg,  Al,  Zr,  Th,  Y,  Gl. 

Fusible  Compounds. — SiO2  effervesces  and  forms  a  clear  bead  that 
remains  clear  on  cooling  if  the  reagent  is  not  in  excess. 

TiO2  effervesces  and  forms  a  clear  yellow  bead  crystalline  and 
opaque  on  cooling- 

WO3  and  MoO3  effervesce  but  sink  in  the  charcoal. 

Ba,  Sr,  Ta,  V,  Nb  sink  into  the  charcoal. 

Ga  fuses,  then  decomposes,  and  the  soda  sinks  into  the  charcoal. 


92  BLOWPIPE   ANALYSIS. 

Colored  Beads.  —  Mn  forms  a  turquois  or  blue-green  opaque 
bead  with  soda  on  platinum  wire  in  the  oxidizing  flame. 

Cr  forms  a  chrome-yellow  opaque  bead  with  soda  on  platinum 
wire  in  the  oxidizing  flame,  which  becomes  green  in  reducing  flame. 

Sulphur  Reaction.  —  If  a  little  of  the  residue,  with  some  of  the 
charcoal  beneath,  is  taken  up  upon  the  point  of  a  knife  and  placed 
upon  a  wet  silver  coin,  the  coin  will  be  blackened  if  sulphur  was 
present  as  a  sulphide.  Sulphates  and  other  sulphur  compounds 
will  also  give  the  same  reaction  after  thorough  fusion.  The  test 
should  always  be  made  on  a  fresh  piece  of  charcoal. 
IV.  With  Metallic  Sodium. 

Reducing  effects  which  are  obtained  with  soda  only  by  hard 
blowing  may  be  accomplished  by  the  use  of  metallic  sodium  im- 
mediately and  with  the  greatest  ease.  The  metal  should  be 
handled  carefully  and  not  allowed  to  come  in  contact  with  water. 
It  should  be  kept  in  small  tightly  closed  bottles,  and  if  kept  cov- 
ered with  naphtha,  which  is  not  necessary,  care  should  be  taken 
that  the  naphtha  is  not  exposed  to  fire. 

A  cube  of  sodium  about  a  quarter-inch  in  diameter  is  cut  off 
with  a  knife  and  hammered  out  flat.  The  powdered  substance  is 
placed  upon  the  sodium,  pressed  into  it  and  the  whole  moulded 
into  a  little  ball  with  a  knife  blade.  This  sodium  ball  should  not 
be  touched  with  the  fingers,  for  if  some  oxides  are  present,  such  as 
lead  oxide,  spontaneous  combustion  may  take  place.  After  plac- 
ing the  sodium  ball  on  the  charcoal  it  should  be  touched  care- 
fully with  a  match  or  with  the  Bunsen  flame.  A  little  flash  ensues 
and  the  reduction  is  accomplished.  The  residue  can  now  be  safely 
heated  with  the  reducing  flame  of  the  blowpipe,  any  reduced  metal 
collected  together  and  the  sodium  compounds  volatilized  or  ab- 
sorbed by  the  charcoal.  When  present  in  sufficient  quantity,  beads 
of  the  malleable  metals  can  be  obtained  immediately  from  almost 
any  of  their  mineral  compounds  ;  metals,  like  zinc  and  tin,  which 
require  reduction  before  volatilization  yield  their  sublimates  with 
comparative  ease  ;  and  if  a  little  of  the  charcoal  beneath  the  assay 
is  placed  on  a  wet  silver  coin  the  sulphur  reaction  will  be  obtained 
if  sulphur  was  present. 

In  general  the  results  are  the  same  as  outlined  for  soda  but  are 
much  more  easily  secured. 

Even  silica,  silicates,  borates,  etc.,  are  reduced  but  are  generally 
identified  by  other  means. 


OPERATIONS   OF  BLOWPIPE  ANALYSIS.  93 

These  reactions  are  not  successful  on  plaster  tablets  on  account 
of  their  non-absorbent  character. 

Tests  in  Closed  Tubes. 

A  plain  narrow  glass  tube  about  4  inches  by  ^  inch  and  closed 
at  one  end  is  best.     The  usual  purposes 
are  to  note   the  effects   of  heat  without 
oxidation,  and  to  effect  fusions  with  such 
reagents  as  KHSO4  or  KC1O3. 

Enough  of  the  substance  is  slid  down 
a  narrow  strip  of  paper,  previously  in- 
serted in  the  tube,  to  fill  it  to  the  height 
of  about  one  half  inch ;  the  paper  is 
withdrawn  and  the  slightly  inclined  tube, 
Fig.  247,  heated  at  the  lower  end  grad- 
ually to  a  red  heat.  The  results  may 
be :  evolution  of  water,  odorous  and 
non-odorous  vapors,  sublimates  of  vari- 
ous colors,  decrepitation,  phosphores- 
cence, fusion,  charring,  change  of  color, 
and  magnetization. 
Acid  or  alkaline  moisture  in  the  upper 

part  of  tube, .         .     H,O. 

Odorless  gas  that  assists  combustion  (nitrates,  chlorates 

and  per  oxides),.          .         .         ....         .     O. 

Pungent  gas  that  whitens  lime  water,         ....     CO2. 

Odors. 

Odor  of  prussic  acid,          .         .         ...         .         .     CN. 

Odor  of  putrid  eggs,          .......     H2S. 

Odor  that  suffocates,  fumes  colorless,  bleaching  action,       .      SOa. 

Odor  that  suffocates,  fumes  violet,  ....  I.* 
fumes  brown,  ....  Br. 
fumes  greenish  yellow,  .  .  Cl, 
fumes  etch  the  glass,  .  .  F. 

Odor  of  nitric  peroxide,  fumes  reddish-brown,          .     NO2. 

Odor  of  ammonia,  fumes  colorless  or  white,    .          .     NH3.f 

*  I,   Br,   Cl,   F  and  N2O5  are  assisted  by   mixing  substance  with  acid  potassium 
sulphate.  f  NH3,  Hg,  As,  Cd  are  assisted  by  mixing  with  soda. 


94 


BLOWPIPE  ANALYSIS. 


Sublimates. 

Sublimate  white,  fusing  yellow PbCl2. 

fusing  to  drops,  disagreeable  odor,  Os. 

and  volatile, NH4  (salts). 

yellow  hot,  infusible,      .         .         .  HgCl. 

yellow  hot,  fusible,         .         .         .  HgCl2. 

fusible,  needle  crystals,  .         .  Sb2O3. 

volatile,  octahedral  crystals,  .         .  As2Os. 

fusible,  amorphous  powder,   .         .  TeO2. 

Sublimate  mirror-like,  collects  in  globules,       .         .  Hg. 

does  not  collect  in  globules,  .  As,  Cd,  Te. 

Sublimate  red  when  hot,  yellow  cold,       .         .  S. 

Sublimate  dark  red  when  hot,  reddish-yellow  cold,  .  As2S3. 

Sublimate  black  when  hot,  reddish-brown  cold,         .  Sb2S3. 

Sublimate  black,  but  becomes  red  when  rubbed,       .  HgS. 
Sublimate   red  to   black,  but   becomes    red   when 

rubbed, Se. 

Color  of  substances  changes 

from  white  to  yellow,  cools  yellow,  .         .         .  PbO. 

from  white  to  yellow,  cools  white,     .          .         .  ZnO. 

from  white  to  dark  yellow,  cools  light  yellow, .  Bi,O3. 

from  white  to  brown,  cools  yellow,  .         .         .  SnO2. 

from  white  to  brown,  cools  brown,   .         .          .  CdO. 
from  yellow  or  red  to  darker,  after  strong  heat, 

cools  green,       ......  Cr2Os. 

from  red  to  black,  cools  red,     ....  Fe2Os. 

from  blue  or  green  to  black,  cools  black,  .  CuO. 

Tests  in  Open  Glass  Tubes. 

FIG.  248.  By  us{ng  a  somewhat  longer 

tube,  open  at  both  ends  and 
held  in  an  inclined  position,  a 
current  of  air  is  made  to  pass 
over  the  heated  substance,  and 
thus  many  substances  not  vola- 
tile in  themselves  absorb  oxy- 
gen and  release  volatile  oxides. 
The  substance  should  be  in 
state  of  powder 

Place  the  assay  near  the  lower 


OPERATIONS    OF  BLOWPIPE  ANALYSIS. 


95 


end  of  the  tube,  Fig.  248,  and  heat  gently, 

creasing   the   air  current  by  holding    the 

nearly  vertical. 

Odor  that  suffocates,  bleaching  action, 

Odor  of  rotten  horseradish, 

Odor  of  garlic, ...... 

Sublimate  white  volatile  octahedral  crystals, 

Sublimate  white  partially  volatile,  fusible 
to  yellow  drops,  pearl  gray  cold, 

Sublimate  white  non-volatile  powder,  dense 
fumes,  ...... 

Sublimate  white  non-volatile  powder,  fu- 
sible to  colorless  drops, 

Sublimate  white  non-volatile  powder,  fusi- 
ble to  yellow  drops,  white  when  cold, 

Sublimate  white  non-volatile  fusible 
powder,  ...... 

Sublimate  gray,  red  at  distance, 

Sublimate  yellow  hot,  white  cold,  crystal- 
line near  the  assay,  blue  in  reducing 
flame,  ...... 

Sublimate  brown  hot,  yellow  cold,  fusible, 

Sublimate  metallic  mirror, 


and  then  strongly,  in- 
tube    more    and  more 

SO2,  indicating  S. 
SeO2, 

As203. 
As203, 

PbOCl, 
Sb203, 
Te02, 
PbS04, 

BiSO4, 
Se02, 


Se. 
As. 
As. 

PbCl,. 
Sb. 
Te. 
PbS. 

BiS. 
Se. 


Mo03,      " 
Bi203,        " 


Mo. 

Bi. 

Hg. 


Bead  Tests  with  Borax  and  with  Salt  of  Phosphorus. 

Preliminary  to  bead  tests,  many  compounds,  sulphides,  arsenides, 
arsenates,  etc.,  may  be  converted  into  oxides  by  roasting  as  follows  : 

Treat  in  a  shallow  cavity  on  charcoal  at  a  dull  red  heat,  never 
allowing  the  substance  to  fuse  or  even  sinter.  Use  a  feeble  oxidiz- 
ing flame  to  drive  off  sulphur,  then  a  feeble  reducing  flame  to 
reduce  arsenical  compounds,  then  reheat  in  an  oxidizing  flame. 
Turn,  crush,  and  reroast  until  no  sulphurous  or  garlic  odor  is 
noticeable. 

Sodium  tetraborate  or  borax  may  be  considered  as  made  up  of 
sodium  metaborate  and  boron  trioxide.  The  boron  trioxide  at  a 
high  temperature  combines  with  metallic  oxides,  driving  out  volatile 
acids,  and  by  the  aid  of  the  oxidizing  flame  the  resulting  borates 
fuse  with  the  sodium  metaborate  to  form  double  borates  which  are 
often  of  a  characteristic  color.  The  color  may  differ  when  hot  and 
cold  and  according  to  the  degree  of  oxidation  and  reduction. 


96  BLOWPIPE  ANALYSIS. 

,.^-^. 

Sodium  ammonium  phosphate,  or  salt  of  phosphorus,  by  fusion 
loses  water  and  ammonia  and  becomes  sodium  metaphosphate. 
The  sodium  metaphosphate  at  high  temperatures  combines  with 
metallic  oxides  to  form  double  phosphates  and  pyrophosphates, 
which  like  the  double  borates  are  frequently  colored,  although  the 
colors  often  differ  from  those  obtained  with  borax. 

A  bead  of  either  flux  is  made  on  platinum  wire  as  described  on 
page  80,  and  the  substance  is  added  gradually  to  the  warm  bead  and 
fused  with  it  in  the  oxidizing  flame.  The  ease  of  dissolving,  effer- 
vescence, color,  change  of  color,  etc.,  should  be  noted. 

We  may  greatly  simplify  the  tabulation  of  results  by  the  follow- 
ing division  : 

1.  Oxides  which  Color  neither  Borax  or  Salt  of  Phosphorus,  or  at 

Most  Impart  a  Pale  Yellow  to  the  Hot  Bead  when  Added 
in  Large  Amounts. 

OXIDES  OF  NOTICEABLE  DISTINCTIONS. 

ALUMINUM.  — Cannot  be  flamed  opaque. 
ANTIMONY.  — Yellow  hot  in  oxidizing  flame,  flamed    opaque 

gray  in  reducing  flame,  on  charcoal  with  tin 

black.     Expelled  by  reducing  flame  in  time. 
BARIUM.       — Flamed  opaque  white. 
BISMUTH.     — Like  antimony. 
CADMIUM.    — Like  antimony,  but  not  made   black  by  fusion 

with  tin. 

CALCIUM.     — Like  barium. 
LEAD.  — Like  antimony,  but  not   made  black    by  fusion 

with  tin. 

MAGNESIUM. — Like  barium. 

SILICON.       — Only  partially  dissolved  in  salt  of  phosphorus. 
STRONTIUM. — Like  barium. 
TIN.  — Like  aluminum. 

ZINC.  — Like    antimony,    but  not  made    black  by  fusion 

Avith  tin. 

2.  Oxides  which  Impart  Decided  Colors  to  the  Beads. 

The  colors  in  hot  and  cold  beads  of  both  fluxes  and  under  both 
oxidation  and  reduction  are  shown  in  the  following  table.  The 
abbreviations  are  :  sat  =  saturated  ;  fl  =  flamed  ;  op  =  opaque. 


OPERATIONS   OF  BLOWPIPE  ANALYSIS. 


97 


Hot  and  cold  relate  to  same  bead  ;  hot  and  cold  to  larger  amounts 
of  the  oxide. 


OXIDES  OF 

VIOLET. 

BLUE. 

GREEN. 

RED. 

BROWN. 

YELLOW. 

COL'L'SS 

Chromium, 

O.F. 
R.F 

cold 
hot,  cold 

hot 

hot 

Cobalt, 

O.F. 

R.F. 

hot,  cold 
hot.  cold 

Copper, 

O.F 
R.F. 

cold 

hot 

Cold(OV.) 

cold 

hot 

Iron, 

O.F. 
R.F. 

hot,  cold 

hot 

hot,  cold 

cold 

Manganese, 

O.F. 
R.F. 

hot  cold 

cold 

hot,  cold 

Molybdenum, 

O.F 
R.F. 

hot  (sat.) 

hot,  cold 

hot 

cold 

Nickel, 

O.F. 

R.F. 

hot 

cold 

hot,  cold 

Titanium, 

O.F 

R.F. 

flamed 

hot,  cold 

hot 

hot,  cold 

hot,  cold 

Tungsten, 

O.F. 
R.F. 

cold 

hot  (sat.) 
hot 

hot,  cold 
cold 

Uranium, 

O.F. 
R.F. 

hot,  cold 

hot 

hot,  cold(fl.) 

Vanadium, 

O.F. 
R.F. 

cold 

hot 

hot.  cold 

hot,  cold 

OXIDES  OF 

VIOLET. 

BLUE. 

GRBEN. 

RED. 

BROWN. 

YELLOW. 

COL'L'SS 

Chromium, 

O.F. 
R.F. 

cold 
cold 

hot 
hot 

Cobalt, 

O.F. 
R.F. 

hot,  cold 
hot,  cold 

Copper, 

O.F. 
R.F. 

cold 
hot 

hot 

cold  (op) 

Iron, 

O.F. 
R.F. 

hot 

hot,  cold 

cold 

cold 

hot,  cold 
hot 

cold 
cold 

Manganese, 

O.F. 
R.F. 

hot,  cold 

hot,  cold 

Molybdenum, 

O.F. 
R.F. 

hot 
hot,  cold 

cold 

Nickel, 

O.F. 
R.F. 

hot 
hot 

cold 
cold 

Titanium, 

O.F. 
R.F. 

cold 

hot 
hot 

hot,  cold 

Tungsten, 

O.F. 
R.F. 

cold 

hot 

hot  (sat.) 

hot,  cold 

Uranium, 

O.F. 

R.F. 

cold 
hot,  cold 

hot 

Vanadium, 

O.F. 
R.F. 

cold 

hot 

hot,  cold 

98  BLOWPIPE  ANALYSIS. 

FLAMING. 

Some  substances  yield  a  clear  glass  with  borax  or  salt  of  phos- 
phorus, which  remains  clear  when  cold,  but  at  a  certain  point  near 
saturation  if  heated  slowly  and  gently  or  with  an  intermittent  flame, 
or  unequally,  or  by  alternate  oxidizing  flame  and  reducing  flame, 
the  bead  becomes  opaque  and  enamel-like. 

The  reason  is  an  incomplete  fusion  by  which  a  part  of  the  base 
is  separated  in  the  crystalline  form. 

Flaming  is  hindered  or  quite  prevented  by  silica.  The  borax 
beads  may  in  general  be  said  to  be  colored  more  intensely  by  equal 
amounts  of  coloring  oxides,  than  the  salt  of  phosphorus  beads 
while  the  latter  may  be  said  to  yield  the  greater  variety  in  color. 

USE  OF  TIN  WITH  BEADS. 

Reduction  is  sometimes  assisted  by  transferring  the  borax  or 
salt  of  phosphorus  bead  to  charcoal  and  fusing  it  for  a  moment 
with  a  grain  or  two  of  metallic  tin.  The  tin  oxidizes  and  takes  its 
oxygen  partly  from  the  oxides  in  the  bead. 

USE  OF  LEAD  AND  GOLD  WITH  BEADS. 

Minute  amounts  of  reduced  metals,  such  as  Cu,  Ni,  Co,  may  be 
collected  from  a  bead  by  fusing  it  on  charcoal  with  a  small  button 
of  lead  or  gold.  The  glass  bead  can  then  be  examined  for  the  non- 
reducible oxides,  and  the  lead  or  gold  can  by  oxidation  in  contact 
with  borax  or  salt  of  phosphorus,  be  made  again  to  yield  oxide 
colors  from  the  reduced  metals. 

Separate  the  button  and  the  slag,  saving  both,  and  heat  the  button 
with  boracic  acid  to  remove  the  lead,  and  then  with  frequently 
changed  S.  Ph.  The  metals  which  have  united  with  the  gold  or 
lead  will  be  successively  oxidized,  and  their  oxides  v/ill  color  the 
S.  Ph.  in  the  following  order  : 

Co. — Blue,  hot;  blue,  cold.     May  stay  in  the  slag. 

Ni. — Brown,  hot ;  yellow,  cold.    May  give  green  with  Co  or  Cu. 

Cu. — Green,  hot ;  blue,  cold.  Made  opaque  red  by  tin  and  re- 
ducing flame. 

The  slag  should  contain  the  more  easily  oxidizable  metals,  and 
be  free  from  Cu,  Ni  and  Ag. 

REDUCTION  COLOR  TESTS. 

Saturate  two  S.  Ph.  beads  with  the  substance  in  the  oxidizing 
flame,  treat  one  of  them  on  charcoal  with  tin  and  strong  reduc- 
ing flame,  pulverize  and  dissolve  separately  in  cold  dilute  (1-4) 


OPERATIONS   OF  BLOWPIPE  ANALYSIS.  99 

hydrochloric  acid  with  the  addition  of  a  little  tin.     Let  the  solu- 
tions stand  for  some  time  and  then  heat  them  to  boiling. 

The  Oxidized  Bead  Yields  The  Reduced  Bead  Yields 

In  Cold  Solution.        In  Hot  Solution.  In  Cold  Solution.        In  Hot  Solution. 

W.          Blue.          Deep  Blue.  Deep  Blue.  Deep  Blue. 

,T        Green  to     ,17.      ^  Faint  Brown  with 

Mo.  Wine  Brown.  Brown. 

Blue.  Black  Precipitate. 

Ti.    Faint  Violet.  YL°le*  and  V;olet  and  Violet, 

lurbid.  Turbid. 

V.    Bluish  Green.    Green.  Green.  Green. 

Cr.         Green.          Green.  Green.  Green. 

U.          Green.  Green.  Green.  Green. 


Tests  with  Sodium  Thiosulphate.  Na.2S2O3. 

A  powdered  metallic  compound  mixed  with  the  dry  flux,  and 
either  heated  in  a  closed  tube  or  upon  a  borax  bead  inside  the 
blue  flame  will  show  the  same  color  as  would  be  produced  by 
passing  H2S  through  a  solution  of  the  compound. 

White  =  Zn.     Orange  =  Sb.     Yellow  =  Cd,  As. 

Brown  =  Sn,  Mo.     Green  =  Cr,  Mn. 

Black  =  Pb,  Fe,  Co,  Cu,  Ni,  Ur,  Bi,  Ag,  Au,  Pt,  Hg. 

Use  of  Acids. 

Acids  are  chiefly  used  in  blowpipe  work  to  expel  and  detect 
volatile  constituents,  to  determine  ease  of  solubility  or  to  assist 
flame  tests. 

Volatile  constituents  are  released  with  bubbling  (effervescence), 
and  the  constituent  is  detected  by  the  odor,  or  sometimes  by 
passing  the  gas  into  another  reagent.  Generally  a  colorless,  odor- 
less gas  shows  the  mineral  to  be  a  carbonate. 

The  mineral  substance  to  be  treated  should  be  ground  to  fine 
powder,  unless  otherwise  stated.      Hydrochloric  acid  is  commonly 
used  but  nitric  acid  is  sometimes  needed  for  metallic  minerals. 
Solubility  may  be  : 

With  effervescence  in  the  cold. 
With  effervescence  only  on  heating. 
Quiet  and  easy. 
Difficult  and  incomplete. 
With  separation  of  perfect  jelly. 


100  BLOWPIPE  ANALYSIS, 

With  separation  of  imperfect  jelly. 
With  separation  of  powder. 
With  separation  of  crystals. 

Tests  with  Cobalt  Solution. 

Cobalt  nitrate  dissolved  in  ten  parts  of  water  is  used  to  moisten 
light  colored  infusible  substances.  These  are  then  heated  to  red- 
ness in  the  oxidizing  flame  and  colored  compounds  result. 

BLUE,  A12O3  and  minerals  containing  it.     Silicates  of  zinc. 

GREEN  (bluish),  SnO2. 

GREEN  (yellowish),  ZnO,  TiO2. 

GREEN  (dark),  oxides  of  antimony  and  columbium. 

FLESH  COLOR,  MgO,  and  minerals  containing  it. 

Test  with  Magnesium  Ribbon. 

Build  a  little  pyramid  of  the  powdered  substance  on  charcoal, 
around  a  half  inch  length  of  magnesium  ribbon  and  ignite  the  rib- 
bon by  touching  with  the  flame  ;  after  the  flash  place  in  water. 

Odor  of  PH3  =  P. 

Tests  with  Acid  Potassium  Sulphate. 

This  reagent  may  be  used  to  decompose  insoluble  compounds 
preparatory  to  wet  separation,  but  its  use  in  blowpipe  analysis  is 
chiefly  to  release  volatile  vapors  and  as  a  component  of  bismuth 
flux  and  boracic  acid  flux. 

COLOR  OF  FUMES.  ODOR.  REMARKS.          INDICATING. 

Brown.  Pungent.  From  nitrates.  NO2. 

Brown.  Choking.  Turn  starch   paper  Br. 

yellow. 

Violet.  Choking.  Turn  starch   paper  I. 

violet. 

Yellowish-green.     Chlorine.  Explosive.  C1O2. 

Colorless.  Burning  sulphur.  SO2. 

Colorless.  Pungent.  Corrodes  the  glass.  HF. 

Colorless.  Chlorine.  White  vapors  with  HC1. 

NHS. 

Colorless.  Bad  eggs.  Blacken  lead  acetate  H2S. 

paper. 

Colorless.  Almonds.  Whitens  lime  water.  HCN. 

Colorless.  Odorless.  Whitens  lime  water.  CO«. 


OPERATIONS   OF  BLOWPIPE  ANALYSIS.  IOI 

Others  of  minor  importance,  acetic  acid,  chromic  acid,  organic 
acids,  etc. 

Tests  with  Potassium  Chlorate. 

Heat  gradually  in  a  matrass  with  the  chlorate  ;  finally  there  will 
be  an  energetic  oxidation,  and  the  fused  mass  will  be: 
Black  =  Ni,  Cu.     Bluish  black  =  Co. 
Purple  =  Mn.     Brown  =  Pb.     Flesh  color  =  Fe. 

Tests  with  Boracic  Acid  Flux. 

Grind  4^  parts  KHSO4,  I  part  CaF2  to  paste  with  water,  add 
substance,  thoroughly  mixing.  Heat  at  tip  of  the  blue  flame.  Just 
after  the  water  is  driven  off  there  may  be  yellow  green  flame  of 
boron,  or  carmine  flame  of  lithia. 

Use  of  Boracic  Acid. 

Is  used  to  separate  lead  and  bismuth  from  antimony,  copper, 
cadmium,  silver,  etc. 


CHAPTER   XII. 
SUMMARY   OF   USEFUL   TESTS   WITH   THE  BLOWPIPE. 

THE  details  of  ordinary  manipulations,  such  as  obtaining  beads, 
flames,  coatings  and  sublimates,  are  omitted  and  the  results  alone 
stated;  unusual  manipulations  are  described.  The  bead  tests 
are  supposed  to  be  obtained  with  oxides ;  the  other  tests  are  true, 
in  general,  of  all  compounds  not  expressly  excluded.  The  course 
to  be  followed  in  the  case  of  interfering  elements  is  briefly  stated. 

ALUMINUM,  Al. 

With  Soda. — Swells  and  forms  an  infusible  compound. 
With  Borax  or  S.  Ph. — Clear  or  cloudy,  never  opaque. 
With  Cobalt  Solution.* — Fine  blue  when  cold. 

AMMONIUM,  NH,. 

In  Closed  Tube. — Evolution  of  gas  with  the  characteristic  odor. 
Soda  or  lime  assists  the  reaction.  The  gas  turns  red  litmus  paper 
blue  and  forms  white  clouds  with  HC1  vapor. 

ANTIMONY,  Sb. 

On  Coal,  R.  F.~\ — Volatile  white  coat,  bluish  in  thin  layers,  con- 
tinues to  form  after  cessation  of  blast  and  appears  to  come  directly 
off  the  mass. 

With  Bismuth  Flux: 

On  Plaster. — Peach-red  coat,  somewhat  mottled. 
On  Coal. — Faint  yellow  or  red  coat. 


*  Certain  phosphates,  borates  and  fusible  silicates   become   blue  in  absence  of 
alumina. 

f  This  coat  may  be  further  tested  by  S   Ph.  or  flame. 

I O2 


USEFUL    TESTS    WITH  THE  BLOWPIPE,  103 

In  Open  Tube. — Dense,  white,  non-volatile,  amorphous  sublimate. 
The  sulphide,  too  rapidly  heated,  will  yield  spots  of  red. 

In  Closed  Tube. — The  oxide  will  yield  a  white  fusible  sublimate 
of  needle  crystals,  the  sulphide,  a  black  sublimate  red  when  cold. 

Flame. — Pale  yellow-green. 

With  S.  Ph. — Dissolved  by  O.  F.  and  fused  on  coal  with  tin  in 
R.  F.  becomes  gray  to  black. 

INTERFERING  ELEMENTS. 

Arsenic. — Remove  by  gentle  O.  F.  on  coal. 

Arsenic  with  Sulphur. — Remove  by  gentle  heating  in  closed 
tube. 

Copper. — The  S.  Ph.  bead  with  tin  in  R.  F.  may  be  momentarily 
red  but  will  blacken. 

Lead  or  Bismuth. — Retard  formation  of  their  coats  by  inter- 
mittent blast,  or  by  adding  boracic  acid.  Confirm  coat  by  flame, 
not  by  S.  Ph. 

ARSENIC,  As. 

On  Smoked  Plaster. — White  coat  of  octahedral  crystals. 

On  Coal. — Very  volatile  white  coat  and  strong  garlic  odor. 
The  oxide  and  sulphide  should  be  mixed  with  soda. 

With  Bismuth  Flux: 

On  Plaster. — Reddish  orange  coat. 
On  Coal. — Faint  yellow  coat. 

In  Open  Tube. — White  sublimate  of  octahedral  cr)'stals.  Too 
high  heat  may  form  deposit  of  red  or  yellow  sulphide. 

In  Closed  Tube. — May  obtain  white  oxide,  yellow  or  red  sul- 
phide, or  black  mirror  of  metal.  If  the  tube  is  broken  and  the 
mirror  heated,  a  strong  garlic  odor  will  be  noticed. 

Flame. —  Pale  azure  blue. 

INTERFERING  ELEMENTS. 

Antimony. — Heat  in  closed  tube  with  soda  and  charcoal,  break 
and  treat  resulting  mirror  in  O.  F.  for  odor. 

Cobalt  or  Nickel.  —  Fuse  in  O.  F.  with  lead  and  recognize  by 
odor. 

Sulphur. — (a)  Red  to  yellow  sublimate  of  sulphide  of  arsenic  in 

closed  tube. 
(b]  Odor  when  fused  with  soda  on  charcoal. 


104  BLOWPIPE  ANALYSIS. 

BARIUM,  Ba. 

On  Coal  with  Soda. — Fuses  and  sinks  into  the  coal. 
Flame. — Yellowish  green  improved  by  moistening  with  HCi. 
With   Borax  or  S.   Ph. — Clear  and  colorless,  can   be  flamed 
opaque-white. 

BISMUTH,  Bi. 

On  Coal. — In  either  flame  is  reduced  to  brittle  metal  and  yields 
a  volatile  coat,  dark  orange  yellow  hot,  lemon  yellow  cold,  with 
yellowish-white  border. 
With  Bismuth  Flux  .•* 

On  Plaster. — Bright  scarlet  coat  surrounded  by  chocolate 
brown,  with  sometimes  a  reddish  border.     The  brown 
may  be  made  red  by  ammonia. f 
On  Coal. — Bright  red  coat  with  sometimes  an  inner  fringe 

of  yellow. 

With  S.  Ph.— Dissolved  by  O.  F.  and  treated  on  coal  with 
tin  in  R.  F.  is  colorless  hot  but  blackish  gray  and  opaque 
cold. 

INTERFERING  ELEMENTS. 

Antimony. — Treat  on  coal  with  boracic  acid,  and  treat  th*    re- 
sulting slag  on  plaster  with  bismuth  flux. 
Lead. — Dissolve  coat  in  S.  Ph.  as  above. 

BORON,  B. 

All  borates  intumesce  and  fuse  to  a  bead. 

Flame. — Yellowish  green.  May  be  assisted  by  :  (a)  Moistening 
with  H,SO4;  (b]  Mixing  to  paste  with  water,  and  boracic  acid 
flux  (4*4  pts.  KHSO^  I  pt.  CaF2) ;  (c)  By  mixing  to  paste  with 
H2SO4  and  NH4F. 

BROMINE,  Br. 

With  S.  Ph.  Saturated  With  CuO. — Treated  at  tip  of  blue  flame, 
the  bead  will  be  surrounded  by  green  and  blue  flames. 
In  Matrass  With  KHSOV — Brown  choking  vapor. 

INTERFERING  ELEMENTS. 

Silver. — The  bromide  melts  in  KHSO4  and  forms  a  blood-red 
globule  which  cools  yellow  and  becomes  green  in  the  sunlight. 

*  Sulphur  2  parts,  potassic  iodide  I  part,  potassic  bisulphate  I  part, 
t  May  be  obtained  by  heating  S.  Ph.  on  the  assay. 


USEFUL    TESTS    WITH   THE  BLOWPIPE.  105 

CADMIUM,  Cd. 

On  Coal R.  F. — Dark  brown  coat,  greenish  yellow  in  thin  layers. 
Beyond  the  coat,  at  first  part  of  operation,  the  coal  shows  a  varie- 
gated tarnish. 

On  Smoked  Plaster  with  Bismuth  Flux. — White  coat  made  orange 
by  (NHJ2S. 

With  Borax  or  S.  Ph. — O.  F.  clear  yellow  hot,  colorless  cold, 
can  be  flamed  milk-white.     The  hot  bead  touched  to 
Na2S2O3  becomes  yellow. 

R.  F.  Becomes  slowly  colorless. 

INTERFERING  ELEMENTS. 

Lead,  Bismuth,  Zinc. — Collect  the  coat,  mix  with  charcoal  dust 
and  heat  gently  in  a  closed  tube.  Cadmium  will  yield  either  a 
reddish  brown  ring  or  a  metallic  mirror.  Before  collecting  coat 
treat  it  with  O.  F.  to  remove  arsenic. 

CALCIUM,  Ca. 

On  Coal  with  Soda. — Insoluble  and  not  absorbed  by  the  coal. 
Flame. — Yellowish  red  improved  by  moistening  with  HC1. 
With  Borax  or  S.  Ph. — Clear  and  colorless,  can  be  flamed  opaque. 

CARBON  DIOXIDE,  CO  . 

With  Nitric  Acid. — Heat  with  water  and  then  with  dilute  acid. 
CO.,  will  be  set  free  with  effervescence.  The  escaping  gas  will 
render  lime-water  turbid. 

With  Borax  or  S.  Ph. — After  the  flux  has  been  fused  to  a  clear 
bead,  the  addition  of  a  carbonate  will  cause  effervescence  during 
further  fusion. 

CHLORINE,  Cl. 

With  S.  Ph.  Saturated  with  CuO.—  Treated  at  tip  of  blue  flame, 
the  bead  will  be  surrounded  by  an  intense  azure-blue  flame. 

On  Coal  with  CuO. — Grind  with  a  drop  of  H2SO4,  spread  the 
paste  on  coal,  dry  gently  in  O.  F.  and  treat  with  blue  flame,  which 
will  be  colored  greenish-blue  and  then  azure-blue. 

CHROMIUM,  Cr. 

With  Borax  or  S.  Ph.— O.  F.  Reddish  hot,  fine  yellow-green 
cold. 


106  BLOWPIPE  ANALYSIS. 

R.  F.  In  borax,  green  hot  and  cold.     In  S.  Ph.  red  hot, 

green  cold. 
With  Soda. — O.  F.  Dark  yellow  hot,  opaque  and  light  yellow 

cold. 
R.  F.  Opaque  and  yellowish-green  cold. 

INTERFERING  ELEMENTS. 

Manganese. — The  soda  bead  in  O.  F.  will  be  bright  yellowish- 
green. 

COBALT,  Co. 

On  Coal,  R.  F. — The  oxide  becomes  magnetic  metal.     The  solu- 
tion in  HC1  will  be  rose-red  but  on  evaporation  will  be  blue. 
With  Borax  or  S.  Ph. — Pure  blue  in  either  flame. 

INTERFERING  ELEMENTS. 

Arsenic. — Roast  and  scorify  with  successive  additions  of  borax. 
There  may  be,  in  order  given :  Yellow  (iron),  green  (iron  and 
cobalt),  blue  (cobalt),  reddish-brown  (nickel),  green  (nickel  and 
copper),  blue  (copper). 

Copper  and  other  Elements  which  Color  Strongly. — Fuse  with 
borax  and  lead  on  coal  in  R.  F.  The  borax  on  platinum  wire  in 
O.  F.  will  show  the  cobalt,  except  when  obscured  by  much  iron 
or  chromium. 

Iron,  Nickel  or  Chromium. — Fuse  in  R.  F.  with  a  little  metallic 
arsenic,  then  treat  as  an  arsenide. 

Sulphur  or  Selenium. — Roast  and  scorify  with  borax,  as  before 
described. 

COPPER,  Cu. 

On  Coal  R.  F. — Formation  of  red  malleable  metal. 

Flame* — Emerald-green  or  azure-blue,  according  to  compound. 

The  azure-blue  flame  may  be  obtained  : 

(a)  By  moistening  with  HC1  or  aqua  regia,  drying  gently  in  O. 
F.  and  heating  strongly  in  R.  F. 

•  (b]  By  saturating  S.  Ph.  bead  with  substance,  adding  common 
salt,  and  treating  with  blue  flame. 

With  Borax f  or  S.  Ph. — O.  F.  Green  hot,  blue  or  greenish- 
blue  cold. 

*  Sulphur,  selenium  and  arsenic  should  be  removed  by  roasting.    Lead  necessitates 
a  gentle  heat. 

f  By  repeated  slow  oxidation  and  reduction,  a  borax  bead  becomes  ruby  red. 


USEFUL    TESTS    WITH  THE  BLOWPIPE.  IO/ 

R.  F.  Greenish  or  colorless  hot,  opaque  and  brownish-red 
cold.     With  tin  on  coal  this  reaction  is  more  delicate. 

INTERFERING  ELEMENTS. 

General  Method* — Roast  thoroughly,  treat  with  borax  on  coal 
in  strong  R.  F.,  and 

If  Button  Forms. — Separate  the  button  from  the  slag,  remove 
any  lead  from  it  by  O.  F.,  and  make  either  S.  Ph.  or  flame 
test  upon  residual  button. 

If  no  Visible  Button  Forms. — Add  test  lead  to  the  borax  fusion, 
continue  the  reduction,  separate  the  button  and  treat  as  in 
next  test.  (Lead  Alloy.) 

Lead  or  Bismuth  Alloys. — Treat  with  frequently  changed  boracic 
acid  in  strong  R.  F.,  noting  the  appearance  of  slag  and  residual 
button. 

Trace. — A  red  spot  in  the  slag. 

Over  One  Per  Cent. — The  residual  button  will  be  bluish-green 
when  melted,  will  dissolve  in  the  slag  and  color  it  red  upon 
application  of  the  O.  F.,  or  may  be  removed  from  the  slag 
and  be  submitted  to  either  the  S.  Ph.  or  the  flame  test. 

FLUORINE,  F. 

Etching  Test. — If  fluorine  is  released  it  will  corrode  glass  in 
cloudy  patches,  and  in  presence  of  silica  there  will  be  a  deposit 
on  the  glass.  According  to  the  refractoriness  of  the  compound 
the  fluorine  may  be  released  : 

(a)  In  closed  tube  by  heat. 

(£)'  In  closed  tube  by  heat  and  KHSO4 

(c)  In  open  tube  by  heat  and  glass  of  S.  Ph. 

With  Cone.  H2SO4  and  Si02. — If  heated  and  the  fumes  condensed 
by  a  drop  of  water  upon  a  platinum  wire,  a  film  of  silicic  acid  will 
form  upon  the  water. 

IODINE,  I. 

With  S.  Ph.  Saturated  with  CuO. — Treated  at  the  tip  of  the  blue 
flame  the  bead  is  surrounded  by  an  intense  emerald-green  flame. 

In  Matrass  with  KHSOV — Violet  choking  vapor  and  brown 
sublimate. 

*  Oxides,  sulphides,  sulphates  are  best  reduced  by  a  mixture  of  soda  and  borax. 


108  BLOWPIPE  ANALYSIS. 

In  Open   Tube  with  Equal  Parts  Bismuth  Oxide,  Sulphur  and 
Soda. — A  brick-red  sublimate. 

With  Starch  Paper. — The  vapor  turns  the  paper  dark  purple. 

INTERFERING  ELEMENTS. 

Silver. — The  iodide  melts  in  KHSO4  to  a  dark  red  globule,  yel- 
low on  cooling,  and  unchanged  by  sunlight. 

IRON,  Fe. 

On   Coal. — R.  F.  Many  compounds  become  magnetic.     Soda 
assists  the  reaction. 

With  Borax* — O.  F.  Yellow  to  red  hot,  colorless  to  yellow  cold. 

R.  F.  Bottle-green.     With  tin  on  coal,  vitriol-green. 
With  S.  Ph. — O.  F.  Yellow  to  red  hot,  greenish  while  cooling, 

colorless  to  yellow  cold. 

R.  F.  Red  hot  and  cold,  greenish  while  cooling. 
State  of  the  Iron. — A  borax  bead  blue  from  CuO  is  made  red  by 
FeO,  and  greenish  by  Fe2O3. 

INTERFERING  ELEMENTS. 

Chromium. — Fuse  with  nitrate  and  carbonate  of  soda  on  pla- 
tinum, dissolve  in  water  and  test  residue  for  iron. 

Cobalt. — By  dilution  the  blue  of  cobalt  in  borax  may  often  be 
lost  before  the  yellow  of  iron. 

Copper. — May  be  removed  from  borax  bead  by  fusion  with  lead 
on  coal  in  R.  F. 

Manganese. — (a)   May  be  faded  from  borax  bead  by  treatment 

with  tin  on  coal  in  R.  F. 
(b)  May  be  faded  from  S.  Ph.  bead  by  R.  F. 

Nickel. — May  be  faded  from  borax  bead  by  R.  F. 

Tungsten  or  Titanium. — The  S.  Ph.  bead  in  R.  F.  will  be  reddish- 
brown  instead  of  blue  or  violet. 

Uranium. — As  with  chromium. 

Alloys,  Sulphides,  Arsenides,  etc. — Roast,  treat  with  borax  on  coal 
in  R.  F.,  then  treat  borax  in  R.  F.  to  remove  reducible  metals. 

LEAD,  Pb. 

On  Coal.\ — In  either  flame  is  reduced  to  malleable  metal  and 


*  A  slight  yellow  color  can  only  be  attributed  to  iron,  when  there  is  no  decided  color 
produced  by  either  flame  in  highly  charged  beads  of  borax  and  S.  Ph. 
•j~  The  phosphate  yields  no  coat  without  the  aid  of  a  flux. 


USEFUL    TESTS    WITH   THE  BLOWPIPE.  109 

yields,  near  the  assay,  a  dark  lemon-yellow  coat,  sulphur-yellow 
cold  and  bluish-white  at  border. 
With  Bismuth  Flux  : 

On  Plaster. — Chrome-yellow  coat,  blackened  by  (NH4)2S. 
On  Coal. — Volatile  yellow  coat,  darker  hot. 
Flame. — Azure-blue. 
With  Borax  or  S.  Ph.— O.  F.  Yellow  hot,  colorless  cold,  flames 

opaque-yellow. 
R.  F.  Borax  bead  becomes  clear,  S.  Ph.  bead  cloudy. 

INTERFERING  ELEMENTS. 

Antimony. — Treat  on  coal  with  boracic  acid,  and  treat  the  re- 
sulting slag  on  plaster  with  bismuth  flux. 

Arsenic  Sulphide. — Remove  by  gentle  O.  F. 

Cadmium. — Remove  by  R.  F. 

Bismuth. — Usually  the  bismuth  flux  tests  on  plaster  are  sufficient. 
In  addition  the  lead  coat  should  color  the  R.  F.  blue. 

LITHIUM,  Li. 

Flame, — Crimson,  best  obtained  by  gently  heating  near  the  wick. 

INTERFERING  ELEMENTS. 

Sodium,  (a]  Use  a  gentle  flame  and  heat  near  the  wick,  (b]  Fuse 
on  platinum  wire  with  barium  chloride  in  O.  F.  The  flame  will  be 
first  strong  yellow,  then  green,  and  lastly,  crimson. 

Calcium  or  Strontium. — As  these  elements  do  not  color  the  flame 
in  the  presence  of  barium  chloride,  the  above  test  will  answer. 

Silicon. — Make  into  a  paste  with  boracic  acid  flux  and  water,  and 
fuse  in  the  blue  flame.  Just  after  the  flux  fuses  the  red  flame  will 
appear. 

MAGNESIUM,  Mg. 

On  Coal  with  Soda. — Insoluble,  and  not  absorbed  by  the  coal. 

With  Borax  or  S.  Ph. — Clear  and  colorless  can  be  flamed  opaque- 
white. 

With  Cobalt  Solution* — Strongly  heated  becomes  a  pale  flesh 
color. 

MANGANESE,  Mn. 

With  Borax  or  S.  Ph.\ — O.  F.  Amethystine  hot,  reddens  on  cool- 


*  With  silicates  this  reaction  is  of  use  only  in  the  absence  of  coloring  oxides.     The 
phosphate,  arsenate  and  borate  become  violet-red. 

t  The  colors  are  more  intense  with  borax  than  with  S.  Ph. 


110  BL  O  WPIPE  ANAL  YSIS. 

ing.    With  much,  is  black  and  opaque.     If  a  hot  bead  is 
touched  to  a  crystal  of  sodium  nitrate  an  amethystine  or 
rose-colored  froth  is  formed. 
R.  F.  Colorless  or  with  black  spots. 

With  Soda. — O.  F.  Bluish-green  and  opaque  when  cold.  Sodium 
nitrate  assists  the  reaction. 

INTERFERING  ELEMENTS. 

Chromium. — The  soda  bead  in  O.  F.  will  be  bright  yellowish- 
green  instead  of  bluish-green. 

Silicon. — Dissolve  in  borax,  then  make  soda  fusion. 

MERCURY,  Hg. 

With  Bismuth  Flux : 

On   Plaster. — Volatile   yellow   and    scarlet   coat.      If  too 

strongly  heated  the  coat  is  black  and  yellow. 
On  Coal. — Faint  yellow  coat  at  a  distance. 

In  Matrass  with  Dry  Soda  or  with  Lit/targe* — Mirror-like 
sublimate,  which  may  be  collected  in  globules. 

MOLYBDENUM,  Mo. 

On  Coal. — O.  F.  A  coat  yellowish  hot,  white  cold,  crystalline 

near  assay. 
R.  F.  The  coat  is  turned  in  part  deep  blue,  in  part  dark 

copper-red. 

Flame. — Yellowish-green. 
With  Borax.— Q.  F.  Yellow  hot,  colorless  cold. 

R.  F.  Brown  to  black  and  opaque. 
With  S.  /%.— O.  F.  Yellowish-green  hot,  colorless  cold.f 

R.  F.  Emerald-green. 

Dilute  (i^)  HCl  Solutions. — If  insoluble  the  substance  may  first 
be  fused  with  S.  Ph.  in  O.  F.  If  then  dissolved  in  the  acid  and 
heated  with  metallic  tin,  zinc  or  copper,  the  solutions  will  be  suc- 
cessively blue,  green  and  brown.  If  the  S.  Ph.  bead  has  been 
treated  in  R.  F.  the  solution  will  become  brown. 


*  Gold-leaf  is  whitened  by  the  slightest  trace  of  vapor  of  mercury. 
•(•  Crushed  between  damp  unglazed  paper  becomes  red,  brown,  purple  or  blue,  ac- 
cording to  amount  present. 


USEFUL    TESTS    WITH  THE  BLOWPIPE.  Ill 

NICKEL,  Ni. 

On  Coal. — R.  F.  The  oxide  becomes  magnetic. 

With  Borax. — O.  F.  Violet  hot,  pale  reddish-brown  cold. 

R.  F.  Cloudy  and  finally  clear  and  colorless. 
With  S.  Ph.—O.  F.  Red  hot,  yellow  cold. 

R.  F.  Red  hot,  yellow  cold.     On  coal  with  tin  becomes 
colorless. 

INTERFERING  ELEMENTS. 

General  Method. — Saturate  two  or  three  borax  beads  with  roasted 
substance,  and  treat  on  coal  with  a  strong  R.  F.  If  a  visible  button 
results,  separate  it  from  the  borax,  aud  treat  with  S.  Ph.  in  the 
O.  F.,  replacing  the  S.  Ph.  when  a  color  is  obtained. 

If  no  visible  button  results,  add  either  a  small  gold  button  or  a 
few  grains  of  test  lead.  Continue  the  reduction,  and  : 

With  Gold. — Treat  the  gold  alloy  on  coal  with  S.  Ph.  in  strong 

O.  F. 

With  Lead. — Scorify  button  with  boracic  acid  to  small  size, 
complete  the  removal  of  lead  by  O.  F.  on  coal,  and  treat 
residual  button  with  S.  Ph.  in  O.  F. 

Arsenic. — Roast  thoroughly,  treat  with  borax  in  R.  F.  as  long  as 
it  shows  color,  treat  residual  button  with  S.  Ph.  in  O.  F. 

Alloys. — Roast  and  melt  with  frequently  changed  borax  in  R.  F. 
adding  a  little  lead  if  infusible.  When  the  borax  is  no  longer 
colored,  treat  residual  button  with  S.  Ph.  in  O.  F. 

NITRIC  ACID,  HN03. 

In  Matrass  with  KHSOV  or  in  Closed  Tube  with  Litharge. — Brown 
fumes  with  characteristic  odor.  The  fumes  will  turn  ferrous  sul- 
phate paper  brown. 

PHOSPHORUS.  P. 

Flame. — Greenish-blue,  momentary.    Improved  by  cone.  H2SO4. 

In  Closed  Tube  with  Dry  Soda  and  Magnesium. — The  soda  and 
substance  are  mixed  in  equal  parts  and  dried,  and  made  to  cover 
the  magnesium.  Upon  strongly  heating  there  will  be  a  vivid  in- 
candescence, and  the  resulting  mass,  crushed  and  moistened,  will 
yield  the  odor  of  phosphuretted  hydrogen. 

POTASSIUM,  K. 

Flame. — Violet,  except  borates  and  phosphates. 


112  BLOWPIPE  ANALYSIS. 

INTERFERING  ELEMENTS. 

Sodium. — (a)  The  flame,  through  blue  glass,  will  be  violet  or 

blue. 
(b}  A  bead  of  borax  and  a  little  boracic  acid,  made  brown 

by  nickel,  will  become  blue  on  addition  of  a  potassium 

compound. 
Lithium. — The  flame,  through  green  glass,  will  be  bluish-green. 

SELENIUM,  Se. 

On  Coal,  R.  F. — Disagreeable  horse-radish  odor,  brown  fumes, 
and  a  volatile  steel-gray  coat  with  a  red  border. 

In  Open  Tube. — Steel-gray  sublimate,  with  red  border,  some- 
times white  crystals. 

In  Closed  Tube. — Dark-red  sublimate  and  horse-radish  odor. 

Flame. — Azure-blue. 

On  Coal  with  Soda. — Thoroughly  fuse  in  R.  F.,  place  on  bright 
silver,  moisten,  crush,  and  let  stand.  The  silver  will  be  blackened. 

SILICON,  Si. 

On  Coal  with  Soda. — With  its  own  volume  of  soda,  dissolves  with 
effervescence  to  a  clear  bead.  With  more  soda  the  bead  is  opaque. 

With  Borax. — Clear  and  colorless. 

With  S.  Ph. — Insoluble.  The  test  made  upon  a  small  fragment 
will  usually  show  a  translucent  mass  of  undissolved  matter  of  the 
shape  of  the  original  fragment. 

When  not  decomposed  by  S.  Ph.,  dissolve  in  borax  nearly  to 
saturation,  add  S.  Ph.,  and  re-heat  for  a  moment.  The  bead  will 
become  milky  or  opaque  white. 

SILVER,  Ag. 

On  Coal. — Reduction  to  malleable  white  metal. 

With  Borax  or  S.  Ph. — O.  F.  Opalescent. 

Cupellation. — Fuse  on  coal  with  i  vol.  of  borax  glass  and  I  to 
2  vols.  of  test  lead  in  R.  F.  for  about  two  minutes.  Remove  button 
and  scorify  it  in  R.  F.  with  fresh  borax,  then  place  button  on  cupel 
and  blow  O.  F.  across  it,  using  as  strong  blast  and  as  little  flame  as 
are  consistent  with  keeping  button  melted. 

If  the  litharge  is  dark,  or  if  the  button  freezes  before  brightening,  of 
if  it  brightens  but  is  not  spherical,  rescorify  it  on  coal  with  borax, 


USEFUL    TESTS    WITH  THE  BLOWPIPE.  113 

add  more  test  lead,  and  again  cupel  until  there  remains  only  a  white 
spherical  button  of  silver. 

SODIUM,  Na. 

Flame. — Strong  reddish-yellow. 

STRONTIUM,  Sr. 

On  Coal  with  Soda. — Insoluble,  absorbed  by  the  coal. 
Flame. — Intense  crimson,  improved  by  moistening  with  HC1. 
With  Borax  or  S.  Ph. — Clear   and   colorless;  can  be  flamed 
opaque. 

INTERFERING  ELEMENTS. 

Barium. — The  red  flame  may  show  upon  first  introduction  of 
the  sample  into  the  flame,  but  it  is  afterward  turned  brownish- 
yellow. 

Lithium. — Fuse  with  barium  chloride,  by  which  the  lithium  flame 
is  unchanged. 

SULPHUR,  S. 

On  Coal  with  Soda  and  a  Little  Borax. — Thoroughly  fuse  in  the 
R.  F.,  and  either  : 

(a)  Place  on  bright  silver,  moisten,  crush  and  let  stand.    The 

silver  will  become  brown  to  black.     Or, 
(b}  Heat  with  dilute  HC1  (sometimes  with  powdered  zinc) ; 

the  odor  of  H2S  will  be  observed. 

In  Open  Tube. — Suffocating  fumes.  Some  sulphates  are  unaf- 
fected. 

In  Closed  Tube. — May  have  sublimate  red  when  hot,  yellow  cold, 
or  sublimate  of  undecomposed  sulphide,  or  the  substance  may  be 
unaffected. 

With  Soda  and  Silica  (equal  parts). — A  yellow  or  red  bead. 
To  Determine  Whether  Sulphide  or  Sulphate. — Fuse  with  soda  on 
platinum  foil.     The  sulphide  only  will  stain  silver. 

TELLURIUM,  Te. 

On  Coal. — Volatile  white  coat  with  red  or  yellow  border.  If 
the  fumes  are  caught  on  porcelain,  the  resulting  gray  or  brown 
film  may  be  turned  crimson  when  moistened  with  cone.  H2SO4, 
and  gently  heated. 


114  BLOWPIPE  ANALYSIS. 

On  Coal  with  Soda. — Thoroughly  fuse  in  R.  F.    Place  on  bright 
silver,  moisten,  crush  and  let  stand.    The  silver  will  be  blackened. 
Flame. — Green. 

In  Open  Tube. — Gray  sublimate  fusible  to  clear  drops. 
With  HzSOi  (cone.). — Boiled  a  moment,  there  results  a  purple 
violet  solution,  which  loses  its  color  on  further  heating  or  on  dilu- 
tion. 

TIN,  Sn. 
On  Coal. — O.  F.  The  oxide  becomes  yellow  and  luminous. 

R.  F.  A  slight  coat,  assisted  by  addition  of  sulphur  or  soda. 
With  Cobalt  Solution. — Moisten  the  coal,  in  front  of  the  assay, 
with  the  solution,  and  blow  a  strong  R.  F.  upon  the  assay.     The 
coat  will  be  bluish-green  when  cold. 

With  CuO  in  Borax  Bead. — A  faint  blue  bead  is  made  reddish- 
brown  or  ruby-red  by  heating  a  moment  in  R.  F.  with  a  tin  com- 
pound. 

INTERFERING  ELEMENTS. 

Lead  or  Bismuth  (Alloys]. — It  is  fair  proof  of  tin  if  such  an  alloy 
oxidizes  rapidly  with  sprouting  and  cannot  be  kept  fused. 

Zinc. — On  coal  with  soda,  borax  and  charcoal  in  R.  F.  the  tin 
will  be  reduced,  the  zinc  volatilized ;  the  tin  may  then  be  washed 
from  the  fused  mass. 

TITANIUM,*  Ti. 
With  Borax. — O.  F.    Colorless  to  yellow  hot,  colorless  cold, 

opalescent  or  opaque- white  by  flaming. 
R.  F.  Yellow  to  brown,  enamel  blue  by  flaming. 
With  S.  Ph.— O.  F.  As  with  borax. 
R.  F.  Yellow  hot,  violet  cold. 

HCl  Solutions. — If  insoluble  the  substance  may  first  be  fused 
with  S.  Ph.  or  with  soda  and  reduced.  If  then  dissolved  in  dilute 
acid  and  heated  with  metallic  tin,  the  solution  will  become  violet 
after  standing.  Usually  there  will  also  be  a  turbid  violet  precipi- 
tate, which  becomes  white. 

INTERFERING  ELEMENTS. 
Iron. — The  S.  Ph.  bead  in  R.  F.  is  yellow  hot,  brownish-red  cold. 

TUNGSTEN,  W. 

With  Borax. — O.  F.  Colorless  to  yellow  hot,  colorless  cold,  can 
be  flamed  opaque-white. 

*  If  the  substance  is  mixed  with  sodium  fluoride,  fused  on  platinum  with  a  little 
sodium  pyrosulphate  and  dissolved  by  boiling  in  a  very  weak  solution  of  sulphuric 
acid,  the  addition  of  a  few  drops  of  hydrogen  peroxide  will  produce  a  color  like  that 
of  ferric  chloride. 


USEFUL    TESTS    WITH  THE  BLOWPIPE.  115 

R.  F.  Colorless  to  yellow  hot,  yellowish-brown  cold. 
With  S.  Ph.—O.  F.  Clear  and  colorless. 

R.  F.  Greenish  hot,  blue  cold.     On  long  blowing  or  with 

tin  on  coal,  becomes  dark  green. 

With  Dilute  HCl. — If  insoluble,  the  substance  may  first  be  fused 
with  S.  Ph.  The  solution  heated  with  tin  becomes  dark  blue  ; 
with  zinc  it  becomes  purple  and  then  reddish-brown. 

INTERFERING  ELEMENTS. 
Iron. — The  S.  Ph.  in  R.  F.  is  yellow  hot,  blood-red  cold. 

URANIUM,  U. 

With  Borax. — O.  F.  Yellow  hot,  colorless  cold,  can  be  flamed 
enamel  yellow. 

R.  F.  Bottle-green,  can  be  flamed  black  but  not  enamelled. 
With  S.  /%.--O.  F.  Yellow  hot,  yellowish-green  cold. 

R.  F.  emerald-green. 

INTERFERING  ELEMENTS. 
Iron. — With  S.  Ph.  in  R.  F.  is  green  hot,  red  cold. 

VANADIUM,  V. 

With  Borax. — O.  F.  Colorless  or  yellow  hot,    greenish-yellow 

R.  F.  Brownish  hot,  emerald-green  cold. 
With  S.  Ph.— O.  F.  Dark  yellow  hot,  light  yellow  cold. 

R.  F.  Brown  hot,  emerald-green  cold. 

HZSO^  Solutions. — Reduced  by  Zn  become  successively  yellow, 
green,  bluish-green,  blue,  greenish-blue,  bluish-violet  and  lavender. 

ZINC,  Zn. 

On  Coal. — O.  F.  The  oxide  becomes  yellow  and  luminous. 

R.  F.  Yellow  coat,  white  when  cold,  assisted  by  soda  and 
a  little  borax. 

With  Cobalt  Solution. — Moisten  the  coal,  in  front  of  the  assay, 
with  the  solution,  and  blow  a  strong  R.  F.  upon  the  assay.  The 
coat  will  be  bright  yellow-green  when  cold. 


Il6  BLOWPIPE  ANALYSIS. 

INTERFERING   ELEMENTS. 

Antimony. — Remove  by  strong  O.  F.,  or  by  heating  with  sulphur 
in  closed  tube. 

Cadmium  Lead  or  Bismuth. — The  combined  coats  will  not  pre- 
vent the  cobalt  solution  test. 

Tin. — The  coats  heated  in  an  open  tube,  with  charcoal  dust  by 
the  O.  F.,  may  yield  white  sublimate  of  zinc. 


CHAPTER   XIII. 
SCHEMES  FOR  QUALITATIVE  BLOWPIPE  ANALYSIS. 

TEST  I.*  — Heat  a  portion  gently  with  0.  F.  upon  charcoal  or  a 
plaster  tablet  which  has  been  blackened  in  the  lamp  flame. 

As.  —  White  very  volatile  crystalline  coat,  white  fumes  having 
garlic  odor  and  invisible  near  assay,  best  on  plaster. 

The  coat  disappears  before  R.  F.,  tingeing  it  pale  blue  and  evolving  the  character- 
istic garlic  odor. 

CONFIRMATION  As.  —  The  coating  may  be  scraped  off  together  with  a  little  charcoal 
and  if  heated  in  closed  tube  should  yield  an  arsenic  mirror  ;  or  it  may  be  dissolved  in 
solution  of  KOH,  placed  in  a  test-tube,  a  small  piece  of  sodium  amalgam  added,  and 
the  tube  covered  with  a  piece  of  filter  paper  moistened  with  a  slightly acid  solution  of 
AgNO3.  The  paper  will  be  stained  black  by  the  AsH3  evolved. 

Sb.  —  White  fumes  and  white  pulverulent  volatile  coat,  best  on 
charcoal. 

A  good  distinguishing  feature  between  As  and  Sb  is  as  follows  :  They  both  usually 
continue  to  give  off  fumes  after  removal  of  the  flame,  but  while  still  hot  the  As,2O3  fumes 
are  not  visible  within  one-half  inch  of  assay,  while  Sb2O4  fumes  appear  to  come  imme- 
diately from  the  mass. 

CONFIRMATION  Sb.  — The  coating  disappears  before  R.  F.,  tingeing  it  a  pale  yel- 
low-green, or,  if  scraped  together,  dissolved  in  S.  Ph.  and  just  fused  on  charcoal  in 
contact  with  tin  it  will  form  a  gray  or  black  opaque  bead. 

If  the  coating  be  scraped  off  and  dissolved  in  tartaric  acid  -|-  HC1,  and  the  solution 
placed  in  a  platinum  capsule  with  a  piece  of  zinc,  Sb,  if  present,  will  give  a  black 
adherent  stain.  This  may  be  confirmed  by  washing  the  stain  with  water,  then  dissolv- 
ing it  in  a  few  drops  of  hot  tartaric  acid  plus  a  drop  or  two  of  HC1  ;  on  adding  H2S,  an 
orange  precipitate  proves  Sb2S3. 

Most  antimony  minerals  leave  a  white  residue  when  treated  with  concentrated  nitric 
acid.  If  this  residue  is  washed  with  water,  dissolved  in  HC1  and  H2S  added,  an  orange 
precipitate  of  Sb2S3  will  be  formed. 

TEST  II.  —  Mix  some  of  the  powdered  substance  with  metallic 
sodiumf  by  means  of  a  knife  blade,  ignite  carefully  on  charcoal 
and  heat  residue  with  blowpipe  flame  to  obtain  coatings  or  to  fuse 
together  any  metallic  particles.  J  Or  mix  a  portion  with  soda  and 


*  Test  I.  may  also  yield  white  coating  of  chlorides  or  lead  sulphate,  or  of  Se  or  Te, 
non-volatile  coatings  of  Sn  or  Zn  near  the  assay,  yellow  hot  and  white  cold ;  yellow 
coatings  of  Pb  or  Bi  ;  crystalline  yellow  and  white  coating  of  Mo  ;  and  deep  brown 
coating  of  Cd.  All  of  these  will  be  detected  with  greater  certainty  by  later  tests. 

•f  Test  II.  may  also  yield  white  coats  from  Pb,  Bi  or  alkalis,  yellow  coats  from  Pb  or 
Bi,  brown  or  red  coats  from  Cu  or  Mo,  and  the  ash  of  the  coal  may  be  white  or  red. 

\  Until  perfectly  familiar  with  metallic  sodium  reaction  always  read  the  precaution 
on  page  92. 

117 


Il8  BLOWPIPE   ANALYSIS. 

a  little  borax  and  heat  strongly  upon  charcoal  with  R.  F.  for  three 
or  four  minutes. 

A.  Volatile  fumes  or  coating  on  charcoal. 

As. — Garlic  odor,  white  fumes  and  a  white  volatile  coat. 

Sb. — White  fumes  and  a  white  volatile  coat. 

Cd. — Dark  brown  volatile  coat,  sometimes  shading  to  greenish- 
yellow  and  usually  surrounded  by  a  variegated  coloration  resem- 
bling the  colors  of  peacock  feathers. 

CONFIRMATION  Cd.— The  coat  forms  at  first  heating,  and,  if  mixed  with  Na2S2Os 
and  fused  in  a  borax  bead,  will  form  a  bright  yellow  mass  of  CdS. 

Zn. — White  not  easily  volatile  coat,  yellow  when  hot. 
Sn. — White  non-volatile  coat  close  to  assay,  yellow  while  hot 
and  usually  small  in  amount. 

CONFIRMATION  Zn  and  Sn. — If  any  coat  forms,  moisten  it  with  cobalt  solution  and 
blow  a  strong  blue  flame  on  the  substance.  The  coatings  from  other  elements  will 
not  prevent  the  cobalt  coloration.  The  zinc  coat  is  made  bright  yellowish-green. 
The  tin  coat  becomes  bluish-green. 

B.  Residue  left  on  charcoal. 

Crush,  pulverize  and  examine  the  residue  for 

i.  Magnetic  particles  ;  2.  Metallic  buttons  ;  3.  On  moist  silver 
coin. 

i .  Collect  any  magnetic  particles  with  the  magnet ;  dissolve  some 
of  the  magnetic  particles  in  a  borax  bead  with  the  0.  F.  Try  also 
effect  of  R.  F. 

Fe. — The  bead  is :  O.  F.  hot,  yellow  to  red ;  O.  F.  cold,  color- 
less to  yellow ;  R.  F.  cold,  bottle-green. 

CONFIRMATION  Fe. — The  magnetic  particles  yield  with  HNO3,  a  brown  solution 
from  which,  after  evaporating  excess  of  acid,  K4FeCy6  throws  down  a  blue  precipi- 
tate. 

Ni.— The  bead  is :  O.  F.  hot,  intense  violet ;  O.  F.  cold,  pale 
brown ;  R.  F.  cold,  colorless. 

CONFIRMATION  Ni. — If  the  excess  of  acid  is  driven  off  by  evaporation,  KCy  added 
in  excess,  and  the  solution  then  made  strongly  alkaline  with  KOH,  two  or  three  drops 
of  pure  bromine  will  give  a  black  precipitate  of  Ni2(OH)6. 

Co.— The  bead  is :  O.  F.  and  R.  F.  hot  or  cold,  a  deep  pure 
blue ;  if  greenish  when  hot,  probably  Fe  or  Ni  is  also  present. 

CONFIRMATION  Co.— The  magnetic  particles  yield  with  HNOS,  a  red-rose  solution 
which  becomes  blue  on  evaporation. 


SCHEMES  FOR    QUALITATIVE  ANALYSIS.  119 

2.  Examine  residue  for  metallic  buttons  and  observe  if  they  are 
malleable  or  not.* 

Ag.  —  Silver  white  malleable  button. 

CONFIRMATION  Ag.  —  Dissolve  button  in  dilute  HNO3,  and  add  a  drop  of  HC1.  A 
white  precipitate,  soluble  in  NH4OH  is  obtained. 

Pb.  —  Lead  gray  malleable  button. 

CONFIRMATION  Pb.  —  With  bismuth  flux  on  charcoal  gives  yellow  coating. 

Sn.  —  White  malleable  button. 

CONFIRMATION  Sn.  —  Heated  in  O.  F.  on  charcoal  gives  a  non-volatile  coating, 
yellow  hot  and  white  cold.  Decomposed  in  cone.  HNOS  with  white  residue  of  meta- 
stannic  acid. 

Cu.  —  Reddish  malleable  button. 

CONFIRMATION  Cu.  —  Dissolves  in  HNOS  to  a  green  solution  rendered  intense  blue 
when  neutralized  with  NH^OH. 

Au.  —  Yellow  malleable  button. 

CONFIRMATION  Au.  —  Insoluble  in  HNO3  or  HC1  alone,  but  dissolved  by  mixed 
acids. 

Bi.  —  Reddish  white  brittle  button. 
CONFIRMATION  Bi.  —  Heat  with  bismuth  flux. 

Sb. — White  brittle  button,  yielding  white  coating  before  the 
blowpipe. 

3.  Dig  up  some  of  the  charcoal  beneath  assay,  place  upon  a  bright 
silver  surface  ;  moisten  with  water  and  let  stand. 

S,  Se,  Te. — The  bright  silver  is  stained  black  or  dark-brown, 
and  unless  the  horseradish  odor  of  Se  or  the  brown  coatings  of 
Se  and  Te  with  bismuth  flux  have  been  already  obtained,  this  stain 
will  prove  sulphur. 

CONFIRMATIONS  S. — The  soda  fusion  will  evolve  H2S  when  moistened  with  HC1. 
By  holding  in  the  gas  a  piece  of  filter  paper  moistened  with  a  drop  or  two  of  lead 
acetate  (test  is  made  more  sensitive  by  adding  a  drop  of  ammonia  to  the  acetate),  the 
paper  will  be  stained  black. 

CONFIRMATION  Se. — Characteristic  disagreeable  horseradish  odor  during  'fusion. 

CONFIRMATIONS  Te.— If  a  little  of  the  original  substance  is  dropped  into  boiling 
concentrated  H2SO4,  a  deep  violet  color  is  produced;  this  disappears  on  further 
heating. 

The  quite  cold  soda  fusion  added  to  hot  water  produces  a  purple-red  solution. 

TEST  III. — Mix  a  portion  of  the  substance  with  more  than 
an  equal  volume  of  bismuth  flux,f  and  heat  gently  upon  a 
plaster  tablet  with  the  oxidizing  flame. 

*  A  white  malleable  button  of  zinc  is  sometimes  obtained  but  not  if  reduction  was 
made  by  soda.     It  is  easily  soluble  in  cold  dilute  hydrochloric  acid  with  effervescence. 
|  Formed  by  grinding  together  I  part  KI,  I  part  KHSO4,  2  parts  S. 


120  BLOWPIPE  ANALYSIS. 

Pb. — Chrome-yellow  coat,  darker  hot,  often  covering  the  entire 
tablet. 

CONFIRMATION  Pb. — If  the  test  is  made  on  charcoal,  the  coat  is  greenish-yellow, 
brown  near  the  assay. 

Hg. — Gently  heated,  bright  scarlet  coat,  very  volatile,  and  with 
yellow  fringe;  but  if  quickly  heated,  the  coat  formed  is  pale  yel- 
low and  black. 

CONFIRMATION  Hg. — If  the  substance  is  heated  gently  in  a  closed  tube  or  matrass 
with  dry  soda  or  litharge,  a  mirror-like  sublimate  will  form,  which  may  be  collected 
into  little  globules  of  Hg  by  rubbing  with  a  match  end.  The  test  with  bismuth  flux 
on  charcoal  yields  only  a  faint  yellow  coat. 

Bi. — Bright  chocolate-brown  coat,  with  sometimes  a  reddish 
fringe. 

CONFIRMATIONS  Bi. — The  coat  is  turned  orange-yellow,  then  cherry-red,  by  fumes 
of  NH3,  which  may  conveniently  be  produced  by  heating  a  few  crystals  of  S.  Ph.  on 
the  assay.  The  test  with  bismuth  flux  on  charcoal  yields  a  bright-red  band,  with 
sometimes  an  inner  fringe  of  yellow. 

Sb. — Orange  to  peach-red  coat,  very  dark  when  hot. 

CONFIRMATION  Sb. — The  coat  becomes  orange  when  moistened  with  (NH4)2S. 

Test  IV.  may  yield  colored  sublimates  with  large  amounts  of  certain  other  elements, 
and  on  smoked  plaster  certain  white  sublimates  are  obtainable.  In  all  cases  the 
elements  are  detected  with  greater  certainty  by  other  tests,  but  for  convenience  they 
are  here  summarized :  Sn,  brownish-orange ;  As,  reddish-orange ;  Se,  reddish-brown ; 
Te,  purplish-brown,  with  deep  brown  border ;  Mo,  deep  ultramarine  blue ;  Cu,  Cd, 
Zn,  white  on  smoked  plaster. 

TEST  IV.— Dissolve  substance  in  salt  of  phosphorus  in  O.  F. 
so  long  as  bead  remains  clear  on  cooling.  Treat  then  for 
three  or  four  minutes  in  a  strong  R.  F.  to  remove  volatile 
compounds.  Note  the  colors  hot  and  cold,  then  re-oxidize 
and  note  colors  hot  and  cold. 

Fe,  Ti,  Mo,  W.— The  bead  in  O.  F.  cold  is  COLORLESS  or  very 

FAINT  YELLOW. 

CONFIRMATION  Fe.— The  bead  in  its  previous  treatment  should  have  been  O.  F. 
hot,  yellow  to  red ;  O.  F.  cold,  colorless ;  R.  F.  cold,  bottle  green. 

CONFIRMATION  Ti. — The  bead  is  reduced  on  charcoal  with  tin,  pulverized  and  dis- 
solved in  \  HC1  with  a  little  metallic  tin.  The  reduced  bead  is  violet,  the  solution  is 
violet  and  turbid. 

CONFIRMATIONS  Mo. — Tested  as  above  on  charcoal  with  tin,  etc.,  the  reduced  bead 
is  green,  the  solution  is  dark  brown.  Heat  a  little  of  the  substance  on  platinum  foil 
with  a  few  drops  of  cone.  HNO,,  heat  until  excess  of  HNO,  has  all  volatilized,  then  add 


SCHEMES  FOR    QUALITATIVE  ANALYSIS.  121 

few  drops  of  strong  H2SO4  and  heat  until  copious  fumes  are  evolved  ;  cool,  and  breathe 
upon  the  cooled  mass ;  an  ultramarine  blue  =  Mo. 

CONFIRMATION  W. — Tested  on  charcoal  with  tin,  etc.,  as  above,  the  reduced  bead 
is  green,  the  solution  is  deep  blue. 

Ur,  V,   Ni.* — The  bead  in  O.  F.  cold,  is  colored  YELLOW  OR 

GREENISH-YELLOW. 

CONFIRMATION  U.— The  bead  in  R.  F.  is  dull  green,  hot ;  fine  green,  cold.  Make 
a  Na.jCO3  fusion,  dissolve  in  HC1  or  H2SO4,  add  a  few  drops  or  H2S  water,  and  if  it 
gives  any  precipitate,  add  it  in  excess  and  filter;  to  filtrate  add  a  few  drops  of  HNO3 
and  boil,  then  add  NH4OH  to  alkaline  reaction,  filter,  wash  precipitate  with  ammonia 
water,  and  then  treat  precipitate  with  a  concentrated  solution  of  (NH4)2COS  -(-  NH^OH, 
filter,  acidify  filtrate  with  HC1,  and  add  K4FeCy6.  Brown  ppt.  =  Ur. 

CONFIRMATION  V. — In  R.  F.  the  bead  will  be  brownish  hot,  fine  green  cold.  Fuse 
substance  with  Na2CO3  in  O.  F.,  and  dissolve  fusion  in  a  few  drops  of  dilute  HjSO^ 
or  HC1,  add  a  piece  of  zinc  and  warm ;  blue  color  changing  to  green  and  finally  vio- 
let =  V. 

CONFIRMATION  Ni.— A  borax  bead  in  O.  F.  will  be  intense  violet,  and  in  R.  F.  will 
be  reddish  hot,  yellow  cold. 

Mn. — The  bead  in  O.  F.,  cold,  is  colored  VIOLET;  if  touched 
while  hot  to  a  crystal  of  nitre,  it  is  made  deep  permanganate  color. 

CONFIRMATION  Mn. — Fused  on  platinum  wire  in  O.  F.,  with  a  paste  of  soda,  and 
nitre,  manganese  yields  an  opaque  bluish-green  bead. 

Cr. — The  bead  in  O.  F.,  cold,  is  colored  GREEN. 

*  If  the  absence  of  Ni  is  not  proved,  or  Co  obscures  the  tests,  dissolve  the  substance 
in  borax  on  charcoal  to  saturation,  and  treat  for  five  minutes  in  hot  R.  F. 

If  a  visible  button  results,  separate  it  from  the  borax,  and  treat  with  S.  Ph.  in  the 
O.  F.,  replacing  the  S.  Ph.  when  a  color  is  obtained. 

If  no  visible  button  results,  add  either  a  small  gold  button  or  a  few  grains  of  test 
lead.  Continue  the  reduction,  and,  if  lead  has  been  used,  scorify  the  button  with  fre- 
quently changed  boracic  acid  to  small  size,  stopping  the  instant  the  boracic  acid  is 
colored  by  Co,  Ni,  or  Cu,  blue,  yellow,  or  red,  respectively. 

Complete  the  removal  of  lead  by  O.  F.  on  coal,  and  treat  as  below. 

Treat  the  gold  alloy,  or  the  residual  button  from  the  lead  alloy,  on  coal,  with  fre- 
quently changed  S.  Ph.,  in  strong  O.  F. 

The  metals  which  have  united  with  the  gold  or  lead,  will  be  successively  oxidized 
and  their  oxides  will  color  the  S.  Ph.  in  the  following  order : 

Co.— Blue,  hot ;  blue,  cold.     May  stay  in  the  slag. 

Ni. — Brown,  hot;  yellow,  cold.     May  give  green  with  Co  or  Cu. 

Cu. — Green,  hot;  blue,  cold.     Made  opaque  red  by  tin  and  R.  F. 

The  slag  should  contain  the  more  easily  oxidizable  metals,  and  be  free  from  Cu, 
Ni,  and  Ag.  Test  a  portion  with  S.  Ph.  and  tin  to  prove  absence  of  Cu.  If  present,  it 
must  be  removed  by  further  reduction  with  lead.  Pulverize  the  slags  and  dissolve  a 
portion  in  S.  Ph.,  and  examine  by  Test  V. 


122  BLOWPIPE  ANALYSIS. 

There  may  be  a  green  bead  from  admixture  of  a  blue  and  a  yellow.  If  Cr  is  not 
proved,  examine  in  such  a  case  for  Ur,  V,  Cr,  etc.,  with  unusual  care. 

CONFIRMATION  Cr. — If  the  substance  is  fused  on  platinum  wire  in  the  O.F.  with  a 
paste  of  soda  and  nitre,  an  opaque  yellow  bead  is  produced  ;  and  if  the  soda  bead  is 
dissolved  in  water,  filtered,  acidified  with  acetic  acid,  and  a  drop  or  two  of  lead 
acetate  added,  a  yellow  precipitate  will  be  formed. 

Co,  Cu. — The  bead  in  O.  F.,  cold,  is  colored  BLUE. 

CONFIRMATION  Co. — The  bead  is  deep  blue,  hot  and  cold,  in  both  flames. 

CONFIRMATION  Cu. — The  bead  is  green,  hot,  greenish-blue,  cold,  and  on  fusion  with 
tin  on  coal  becomes  opaque  brownish-red. 

With  larger  percentage  of  copper,  the  substance  will  yield  a  mixed  azure-blue  and 
green  flame  on  heating  with  HC1. 

SiO2,  A12O3,  TiO,,  SnO2 — The  saturated  bead  contains  an  ap- 
preciable amount  of  INSOLUBLE  MATERIAL,  in  the  form  of  a  trans- 
lucent cloud,  jelly-like  mass,  or  skeleton  form  of  the  original 
material. 

CONFIRMATION  SiO2. — Mix  the  dry  substance  with  a  little  dry  calcium  fluoride 
free  from  SiOj,  place  in  a  dry  test  tube  and  add  cone.  H2SO<  and  heat  gently,  hold 
in  fumes  given  off,  a  drop  of  water  in  loop  of  platinum  wire  ;  SiO2  will  be  separated 
on  coming  in  contact  with  the  water  and  form  a  jelly-like  mass. 

Silica  or  silicates  fused  with  soda  unite  with  noticeable  effervescence. 

CONFIRMATION  AL,O3,  TiO2,  SnO2,  SiO2.— If  infusible,  moisten  the  pulverized 
mineral  with  dilute  cobalt  nitrate  solution  and  heat  strongly. 

A1,OS.— Beautiful  bright  blue. 

TiOj.— Yellowish  green. 

SnO,  —  Bluish  green. 

SiOj.— Faint  blue ;  deep  blue,  if  fusible. 

There  may  also  be  blues  from  fusible  phosphates  and  borates,  greens  from  oxides 
of  Zn,  Sb,  violet  from  Zr,  various  indefinite  browns  and  grays,  and  a  very  character- 
istic pale  pink  or  flesh  color  from  Mg. 

CONFIRMATION  SnO2. — Treat  the  finely  pulverized  mineral  with  Zn  and  HC1  in 
contact  with  platinum.  Dissolve  any  reduced  metal  in  HC1  and  test  with  HgCl2. 
There  will  be  white  or  gray  ppt. 

Ba,  Ca,  Sr,  Mg. — The  saturated  bead  is  WHITE  and  OPAQUE 
and  the  nearly  saturated  bead  can  be  flamed  white  and  opaque. 

CONFIRMATION  Ba,  Ca,  Sr. — Moisten  the  flattened  end  of  a  clean  platinum  wire 
with  dilute  hydrochloric  acid,  dip  it  in  the  roasted  substance,  and  heat  strongly  at  the 
tip  of  the  blue  flame,  and  gently  near  the  wick.  Remoisten  with  the  acid  frequently. 

Ba. — Yellowish-green  flame,  bluish-green  through  green  glass. 

Ca. — Yellowish-red  (brick-red)  flame,  green  through  green  glass. 

Sr. — Scarlet-red  flame,  faint  yellow  through  green  glass. 

There  may  also  be  produced  Li,  carmine-red  flame,  invisible  through  green  glass. 


SCHEMES  FOR    QUALITATIVE  ANALYSIS.  123 

K,  rose-violet  flame,  reddish-violet  through  blue  glass.  Na,  orange -yellow  flame, 
invisible  through  blue  glass.  Cu.  azure-blue  and  emerald  green.  Se  and  As,  pale 
blue.  Mo,  Sb,  Te,  pale  green. 

CONFIRMATION  Mg. — Moisten  the  roasted  substance  with  cobalt  solution,  and  heat 
strongly.  The  substance  will  be  colored  pale  pink  or  flesh  color,  or  violet  if  present 
as  either  arsenate  or  phosphate  or  borate. 

TEST  V. — Cupellation  for  silver  and  gold.  Fuse  one  vol. 
of  the  roasted  substance  on  charcoal  with  i  vol.  of  borax  glass, 
and  i  to  2  vols.  of  test  lead  in  R.  F.  for  about  two  minutes. 
Remove  button  and  scorify  it  in  R  F.  with  fresh  borax,  then 
place  button  on  cupel  and  blow  O.  F.  across  it,  using  as  strong 
blast  and  as  little  flame  as  are  consistent  with  keeping  the 
button  melted.  If  the  litharge  is  dark,  or  if  the  button  freezes 
before  brightening,  or  if  it  brightens  but  is  not  spherical,  re- 
scorify  it  on  charcoal  with  borax,  add  more  test  lead,  and 
again  cupel  until  there  remains  only  a  bright  spherical  button 
unaltered  by  further  blowing. 

Ag. — The  button  is  white. 

Au. — The  button  is  yellow  or  white. 

CONFIRMATION  Ag  AND  Au. — Dissolve  in  a  drop  of  HNOS,  and  add  a  drop  of 
HC1,  producing  a  white  curd-like  precipitate.  If  gold  is  present  there  will  be  a  resi- 
due insoluble  in  HNOS  which  will  become  golden  yellow  on  ignition. 

TEST  VI. — Heat  substance  in  matrass  with  acid  potassium 
sulphate. 

N3O5,  Br. — Reddish  brown  vapor. 

CONFIRMATION  N2O5. — The  gas  turns  ferrous  sulphate  paper  brown.  Nitrates  defla- 
grate violently  when  fused  on  charcoal. 

Cl. — Colorless  or  yellowish  green  vapor,  with  odor  of  chlorine. 
I. — Violet  choking  vapor. 

CONFIRMATION  Br,  Cl,  I. — Saturate  a  salt  of  phosphorus  bead  with  CuO,  add  sub- 
stance, and  treat  in  O.  F.  Br,  azure  blue  and  emerald  green  flame.  Cl,  azure  blue 
flame  with  a  little  green.  I,  emerald  green  flame. 

Fuse  with  Na2CO3,  pulverize  and  mix  with  MnO8,  and  add  a  few  drops  of  cone. 
H2SO4,  and  heat.  Cl,  yellowish  green  gas  that  bleaches  vegetable  colors.  Br,  red 
fumes. 

Fuse  with  Na2COs,  dissolve  in  water,  make  slightly  acid  with  H2SO4,  and  add 
Fe2(SOi)s  (ferric  alum  may  be  used),  and  boil;  I,  violet  fumes  (turn  starch  paper 
blue). 


124  BLOWPIPE   ANALYSIS. 

F. — The  glass  of  the  matrass  is  corroded,  and  if  SiO2  is  present 
a  film  of  SiO2  is  often  deposited  on  the  glass. 

CONFIRMATION  F. — If  the  substance  be  mixed  with  silica  and  then  heated  with 
Concentrated  sulphuric  acid,  and  the  fumes  caught  on  a  drop  of  water  held  in  a  loop  of 
platinum  wire,  gelatinous  silica  will  form  in  the  water. 

TEST  VII. — Heat  the  substance  gently  with  water  to  re- 
move air  bubbles  and  then  with  dilute  hydrochloric  acid. 

CO2. — Effervescence  continuing  after  heat  is  removed. 

H2S,  Cl  and  H  are  sometimes  evolved,  but  usually  the  odor  will  distinguish 
these. 

CONFIRMATION  CO.,. — If  the  gas  is  passed  into  lime  water,  a  white  cloud  and  ppt. 
will  be  produced. 

TEST  VIII. -Place  a  piece  of  Mg  wire  in  a  closed  tube,  and 
cover  the  wire  -with  a  mixture  of  soda  and  the  substance. 
Heat  till  the  mass  takes  fire,  cool  and  add  water. 

P. — Evolution  of  phosphine,  recognized  by  odor. 

CONFIRMATION  P. — Fuse  a  little  of  the  substance,  previously  roasted  if  it  contains  As, 
with  two  or  three  parts  Na2CO3  and  one  of  NaNO3  dissolve  in  HNOS,  and  add  excess  of 
(NH4)2MoO4;  yellow  ppt.  =  P2O5.  In  presence  of  SiO2  it  is  well  to  confirm  this  ppt. 
by  dissolving  it  in  dilute  NH4OH,  allowing  it  to  stand  for  half  an  hour  and  filtering 
off  any  SiO2  that  separates,  then  to  filtrate  adding  magnesia  mixture  (MgCl2  + 
NH4C1  +  NH4OH) ;  white  ppt.  =  P.p6. 

Phosphates  yield  a  pale  momentary  bluish  green  flame  when  moistened  with  con- 
centrated H2SO4  and  treated  at  the  tip  of  the  blue  flame. 

TEST  IX.— Make  a  paste  of  four  parts  KHSO4,  one  part  CaF2, 
water  and  substance.  Treat  at  tip  of  blue  flame.  Just  after 
water  is  driven  off  the  flame  will  be  colored. 

B. — Bright  green. 
Li. — Carmine. 

CONFIRMATION  B.  —  Heat  some  of  the  substance  gently  on  platinum  wire,  then  add 
a  drop  of  concentrated  H2SO4,  heat  very  gently  again,  just  enough  to  drive  off  exces 
of  H2SO4,  dip  in  glycerine,  hold  in  flame  until  glycerine  begins  to  burn,  remove  from 
flame,  and  the  mass  will  continue  burning  with  a  green  flame.  Turmeric  paper,  moist- 
ened with  an  HC1  solution  containing  boron  and  dried  at  100°,  is  turned  a  reddish 
brown  which  ammonia  blackens. 

TEST  X.  —  Make  a  paste  of  the  powdered  substance  with  strong 
HC1.  Treat  on  platinum  wire  in  the  non-luminous  flame  of  a 
Bunsen  burner.  Confirm  results  by  the  spectroscope  as  directed  on 
page  87. 


SCHEMES  FOR    QUALITATIVE  ANALYSIS.  125 

The  color  imparted  to  the  flame  is  : 

Alone.  Through  blue  glass. 

Na,  Yellow.  Invisible  or  pale  blue. 

K,  Violet.  Reddish  violet. 

Na  and  K,  Yellow.  Reddish  violet. 

Ba,  Mo,  B,  Yellowish  green.  Bluish  green. 

Ca,  Red.  Greenish  gray. 

Sr,  Scarlet.  Violet. 

Azure  blue,         \  (  Azure  blue. 


Emerald  green,  j        [  Emerald  green. 
TEST  XI.  —  Heat  the  substance  in  a  closed  tube.* 

H.,0.  —  Moisture  on  the  side  of  tube. 

Hg.  —  Metallic  mirror  collecting  in  globules. 

As.  —  Metallic  mirror  but  no  globules. 

TEST  XH.f  —  Treat  the  finely  powdered  substance  in  a  test-tube 
with  strong  HC1.  Observe  the  result,  then  boil. 

Effervescence.  —  If  the  substance  is  non-metallic  the  gas  given 
off  will  almost  always  be  CO2  showing  that  the  substance  was  a 
carbonate.  H2S  is  easily  recognized  by  its  odor.  Cl  which  is 
yellowish  and  very  offensive  would  be  given  off  only  in  a  few  cases 
by  the  action  of  some  oxides  on  HC1. 

CONFIRMATION  C02.  — A  drop  of  lime  water  on  the  end  of  a  glass  rod  held  in  the 
gas  after  it  has  been  passed  through  water  to  free  it  from  HC1  will  be  rendered  turbid. 

CONFIRMATION  H2S.  — A  piece  of  filter  paper  moistened  with  lead  acetate  will  be 
blackened  if  held  in  the  gas. 

CONFIRMATION  Cl.  — A  piece  of  moistened  red  litmus  paper  held  in  the  gas  will  be 
bleached. 

Gelatinous  Residue.  —  If  a  gelatinous  residue  forms  after  boiling 
away  the  larger  part  of  the  acid  a  silicate  was  present. 

*  Other  sublimates  may  result  as  noted  on  page  94. 
•f  Substitute  for  test  VII.  when  convenient. 


126  BLOWPIPE  ANALYSIS. 

SPECIAL    SCHEME    FOR    DETECTION   OF  THOSE 
METALS  WHICH  WHEN  PRESENT  AS  SILI- 
CATES   USUALLY     FAIL    TO    YIELD 
SATISFACTORY  TESTS  BEFORE 
THE  BLOWPIPE. 

Remove  the  volatile  constituents  as  thoroughly  as  possible  by 
roasting,  then  heat  gently  in  a  platinum  capsule,  with  HF  and  a 
few  drops  of  concentrated  H2SO4  as  long  as  fumes  are  given  off; 
add  a  little  more  HF  and  H2SO4,  and  heat  again  in  the  same  way. 
When  fusion  is  quite  cold,  dissolve  in  cold  water  and  filter. 

Filtrate  a. — Divide  into  four  parts  and  test  as  follows : 

1.  Add  a  piece  of  Zn  or  Sn  and  a  little  HC1,  and  heat. 
Ti. — A  violet  or  blue  solution. 

CONFIRMATIONS  Ti.— Nearly  neutralize  solution,  and  then  add  Na2S2O3,  and  boil. 
White  ppt.  =  Ti. 

Or,  make  solution  slightly  alkaline,  and  then  acidify  slightly  with  HC1,  and  add 
Na2HPO4.  White  ppt.  =  Ti. 

2.  Add  excess  of  KOH  or  NaOH,  boil  and  filter,  and  to  filtrate 
add  excess  of  NH4C1.  and  boil. 

Al. — White  precipitate. 

Dissolve  ppt.,  produced  by  the  KOH  or  NaOH,  in  HC1,  and 
add  K4FeCy6. 

Fe. — Blue  precipitate. 

3.  Add  HC1 ;  then  make  alkaline  with  NH4OH  and  add  (NH4\S 
+  (NH4)2CO3  in  slight  excess,  filter;  to  filtrate  add  Na2HPO4. 

Mg. — White  crystalline  precipitate. 

CONFIRMATION  Mg. — If  phosphates  are  present,  this  test  would  not  be  reliable  for 
Mg.  In  such  cases  test  a  few  drops  of  the  solution  with  H2S;  if  it  causes  any  precipi- 
tate, saturate  the  whole  of  the  solution  with  it,  filter,  and  to  filtrate  add  a  few  drops 
of  HNO,,  and  boil  to  oxidize  FeO,  nearly  neutralize  with  solution  of  Na2CO3.  If 
iron  is  not  present,  add  a  few  drops  of  FeaCl6,  enough  to  give  a  red  precipitate  with 
the  sodium  acetate,  then  dilute  and  add  excess  of  sodium  acetate,  and  boil,  filter,  and 
to  filtrate  add  NH4OH  4-  (NH4)2S,  filter,  to  filtrate  add  Na^HPO,.  White  crystalline 
precipitate  =  Mg. 

4.  Add  BaCl2  as  long  as  it  gives  a  precipitate,  then  Ba(OH)2  to 
alkaline  reaction,  boil,  filter,  and  to  filtrate  add  (NH4)2CO3  and 
NH4OH  and  heat,  filter;  evaporate  filtrate  to  dryness  and  ignite 
to  drive  out  NH4  salts.     Test  residue  in  flame  for  K  and  Na ;  dis- 
solve residue  in  a  few  drops  of  water,  filter  if  necessary,  and  then 
add  solution  of  PtQ4  and  alcohol. 


SCHEMES  FOR    QUALITATIVE  ANALYSIS.  1 27 

K.  —  Yellow  crystalline  precipitate. 

CONFIRMATION  Na,  K.— Mix  I  part  of  the  silicate  with  5-6  parts  of  precipitated 
CaCO3  and  I  part  of  NH4C1,  heat  to  redness  in  platinum  capsule  for  thirty  minutes 
being  careful  to  apply  heat  gently  at  first,  digest  sintered  mass  in  hot  water,  and  filter ; 
to  filtrate  add  (NH4)2CO3  and  NH4OH,  heat  and  filter,  evaporate  filtrate  to  dryness  and 
ignite  gently  until  all  ammonium  salts  are  driven  off,  then  determine  Na  and  K  as 
above. 

Residue  a — Boil  with  strong  solution  of  (NH4)2SO4  and  filter. 

Filtrate  b. — Add  a  few  drops  of  H4S  water;  if  any  precipitate 
forms,  saturate  with  H2S  and  filter,  and  to  filtrate  add  NH4OH 
and  (NH4)2C2O4. 

Ca. — A  white  precipitate. 

Residue  b. — Moisten  with  concentrated  HC1  and  try  coloration 
of  flame. 

Ba. — Yellowish-green  flame. 

Sr.— Scarlet  flame. 

CONFIRMATION  Ba  and  Sr. — Fuse  residue  b  with  two  to  three  pts.  of  soda  in  a  pla- 
tinum capsule  :  treat  fusion  with  boiling  water,  filter,  reject  filtrate,  dissolve  residue 
in  acetic  acid,  add  a  few  drops  of  H2S  water,  if  it  gives  any  precipitate,  saturate  with 
H2S  and  filter,  and  to  filtrate  add  K2Cr2O7.  Ba  =  yellow  precipate.  Filter,  and  to 
filtrate  add  CaSC\  warm  and  let  stand.  Sr  =  white  precipitate. 


PART  III. 


DESCRIPTIVE  MINERALOGY. 


CHAPTER   XIV. 

DESCRIPTIVE  TERMS. 
Definition  of  Minerals. 

The  solid  crust  of  the  earth  is  composed  principally  of  "minerals  " 
each  mineral  being  a  homogeneous  substance  of  definite  chemical 
composition,  found  ready-made  in  nature,  and  not  directly  a  product 
/  of  the  life  or  the  decay  of  an  organism. 

Chemical  Salts. 

The  line  is  arbitrarily  drawn  The  manufactured  chemical  sub- 
stance is  not '  a  mineral  although  the  chemist's  laboratqry  and 
Nature  employ  the  same  forces  and  produce  some  substances 
identical  in  all  respects. 

Natural  substances  are  usually  not  easily  imitated  because  the  important  element  of 
long  periods  of  time  cannot  be  given  to  the  manufacture  of  the  substance.  On  the  other 
hand  most  manufactured  compounds  are  too  soluble  and  perishable  to  exist  long  as 
natural  salts. 

Natural  Substances  of  Organic  Origin. 

Materials  which  have  formed  part  of  living  organisms,  coal, 
chalk,  pearls,  coral,  shells,  etc.,  are  not  minerals.  If  by  natural 
agencies  their  organic  structure  is  lost  and  a  new  crystalline  struc- 
ture obtained  they  become  minerals.  That  is  their  components 
may  recombine  or  combine  with  other  elements  to  form  minerals. 

Rocks. 

A  rock  is  a  mineral  mass  which  for  a  considerable  depth  and 
area  is  of  fairly  constant  character.  It  sometimes  consists  entirely 
of  one  mineral,  much  more  frequently  of  two  or  more  minerals, 
and  may  consist  in  part  of  organic  remains. 

128 


DESCRIPTIVE    TERMS.  129 

The  resolution  of  these  rocks  into  their  component  minerals  and  the  study  of  these 
minerals  belong  to  Mineralogy.  The  study  of  these  rocks,  as  such,  is  referred  to 
Petrography  and  Geology. 

The  Study  of  Minerals  or  "  Mineralogy." 

Mineralogy  considers  the  one  thousand  or  so  definite  minerals 
and  the  many  thousands  of  varieties  and  doubtful  species  which 
constitute  the  solid  crust  of  the  earth.  Its  purpose  is  the  study  of 
all  the  qualities  of  these  minerals  ;  their  chemical  composition  as 
revealed  by  analyses ;  their  molecular  structure  as  revealed  by 
crystalline  form  and  by  physical  tests,  and  their  origin  and  mode 
of  formation  as  revealed  by  associated  minerals,  the  alterations 
which  they  undergo  and  their  synthetic  production. 

In  elementary  work  in  mineralogy,  especially  in  a  technical 
course,  the  principal  object  is  the  acquisition  of  an  "  eye  knowledge," 
of  the  common  and  commercially  important  minerals  so  that  they 
may  be  recognized  at  sight  or  determined  rapidly  by  a  few  simple 
tests.  This  knowledge  can  be  acquired  only  by  handling  and  test- 
ing many  labelled  and  unlabelled  specimens,  and  is  best  preceded 
by  a  thorough  drill  in  the  use  of  the  blowpipe  and  a  study  of 
models  and  natural  crystals.  With  this  there  should  be  gained  a 
knowledge  of  their  characters,  economic  uses  and  occurrence. 

A  Mineral  Species. 

No  one  character  will  determine  a  species,  but  chemical  compo- 
sition and  crystalline  form  together  will  do  so,  for  it  is  found  that 
whenever  both  of  these  characters  are  constant  in  different  speci- 
mens, or  vary  only  in  accordance  with  known  laws,  then  all  other 
important  characters  *  are  constant  and  the  specimens  belong  to 
the  same  species. 

The  Two  Conditions  in  Which  Minerals  May  Occur. 

The  Crystalline  Condition.  —  A  mineral  is  sometimes  defined  as 
a  natural  crystal,  that  is,  being  a  chemical  substance,  it  should 
possess  a  crystalline  structure  and  occur  either  in  crystals  of  char- 
acteristic shapes  or  in  masses  made  up  of  many  little  crystals  so 
crowded  together  that  the  shapes  are  not  evident. 

In  the  crystal  and  in  each  grain  of  the  aggregation  the  crystal- 
line structure  will  be  shown  by  the  constancy  of  the  properties  in 
parallel  directions  and  their  variation  in  directions  not  parallel. 

*  Structure,  habit,  color  and  form  of  aggregation  are  considered  non-essential  char- 
acters. 
9 


130 


DESCRIPTIVE  MINERALOGY. 


The  Amorphous  Condition.  — A  few  glassy  and  earthy  minerals 
have  never  been  found  in  crystals  and  in  the  mass  fail  to  show  any 
regular  crystalline  structure.  Opal  is  the  best  example.  Such 
minerals  are  said  to  be  amorphous.  The  number  is  very  small, 
but  certain  varieties  of  minerals  which  crystallize  may,  from  rapid 
cooling  or  other  cause,  be  apparently  amorphous. 

Habit. 

Although,  as  previously  explained,  the  angles  and  forms  which 
occur  on  different  crystals  of  any  substance  are  fixed  and  charac- 
teristic, the  prevailing  conditions  at  formation  may  cause  more 
rapid  growth  in  one  direction  than  another.  The  term  habit  is 
used  to  express  this  relative  development  of  the  faces  as  distin- 
guished from  form  or  forms  which  may  be  exactly  the  same  while 
the  habit  is  very  different. 

The  principal  terms  of  habit  are  : 

Prismatic.  —  Notably  elongated  in  one  direction  whether  that  is 
the  direction  of  the  prism  or  not. 

Tabular.  —  Two  parallel  faces  are  much  larger  than  the  others. 

Pyramidal.  —  The  dominant  faces  meet  in  a  point  or  a  pair  of 
opposite  points. 

Acicular.  —  In  long  thin  needle-like  crystals. 

Capillary.  —  In  hair-like  or  thread-like  crystals. 

Irregularities  of  Faces  of  Crystals. 

The  perfectly  smooth  and  plane  crystal  face  is  difficult  to  find, 
except  in  very  minute  crystals. 

Striated  Faces.  —  Crystal  faces  are  frequently  marked  by  parallel 


FIG.  249. 


FIG.  250. 


lines   or  fine   "  grooves "   called   "  striations,"    each   of  which  is 
bounded  by  two  definite  planes.     They  may  result  from  : 

i .   An  oscillation  or  contest  between  two  crystal  forms  as  in  the 


DESCRIPTIVE    TERMS. 


case  of  the  striations  on  the  prism  faces  of  quartz,  Fig.  249,  which 
are  due  to  an  alternate  formation  of  prism  and  rhombohedron  ;  or 
the  striations  on  pyrite  due  to  an  oscillation  between  the  cube 
and  the  pyritohedron,  Fig.  251. 

2.  A  repeated  twinning  of  small  individuals  which  together  make 

FIG.   251. 


Striated  Pyrite,  Aspen,  Col.     After  S.  Smillie. 

the  whole  crystal.  If  the  individuals  are  thin  the  reentrant  angles 
become  grooves  or  striations.  Fig.  250  shows  twinning  striations 
on  a  magnetite  crystal  from  Port  Henry,  N.  Y.* 

Drusy  Faces.  —  Closely  covered  with  minute  crystals,  giving  a 


FIG.  252. 


FIG.  253. 


rough  surface  like  sandpaper.     Often  showing  by  their  simulta- 
neous glistening  that  they  are  parallel. 

Curved  Faces.  —  Crystals  may  appear  curved  because  composed 
of  individual  smaller  crystals  only  approximately  parallel,  as  in 
dolomite,  or  siderite.  Sometimes  there  result  from  this  cause  very 

*  Fig.  195  shows  coarser  repeated  twinning  on  albite. 


I32 


DESCRIPTIVE  MINERALOGY. 


peculiar  shapes  as  in  the  worm-shaped  crystal  of  corundum,*  Fig. 
252,  which  is  composed  of  layers,  each  a  hexagonal  pyramid  cut 
off  by  the  basal  pinacoid.  At  other  times  the  curving  may  be 
due  to  pressure  after  formation,  which  may  be  accompanied  by  a 
breaking  of  the  crystal  as  in  the  tourmaline,  Fig.  253. 

Curvature  of-  faces  is  often  due  to  a  series  of  vicinal  faces  each 
nearly  parallel  to  the  preceding. 

Vicinal  Faces. — Often  prominent  faces  with  simple  indices  are 
replaced  wholly  or  in  part  by  flattened  pyramids,  the  faces  of  which 
do  not  obey  the  law  of  rational  indices.  The  angles  of  these  vary 
in  different  crystals.  They  seem  to  result  whenever  there  is  a 
rapid  deposition,  but  at  the  same  time  concentration  currents  which 
are  too  feeble  to  completely  cover  the  larger  faces. 

They  are  of  importance  because,  like  etch  figures,  they  usually 
belong  to  forms  which  prove  the  true  symmetry  of  the  crystal 
rather  than  to  the  simple  forms  common  to  several  classes. 

Corroded  and  Etched  Faces.  —  The  faces  are  often  corroded  by 
natural  agencies,  and  many  show  natural  etch  figures  similar  to 
the  artificial  etch  figures  described  on  p.  148. 

Hollow  Crystals.  —  Rapid  growth  may  result  in  deep  depres- 
sions on  each  face,  giving  hopper  shaped  or  skeleton  crystals. 

Inclusions.  —  Foreign  substances  may  be  shut  in  a  crystal  during 
rapid  solidification,  as  in  the  case  of  drops  of  water  or  bubbles  of 


FIG.  254. 


FIG.   255. 


gas  in  quartz,  or  of  sand  in  the  crystals  of  calcite  called  Fontaine- 
bleau  limestone,  Fig.  254,  which  while  retaining  a  form  proper  to 
calcite,  contains  sometimes  as  much  as  sixty  per  cent,  of  silica. 


*  H.    Barvir,   Beitrage  zur  Morphologic  des  Korund,  Ann.   K.   K.   Hofmuseums, 
VII.,  1892,  p.  141. 


DESCRIPTIVE    TERMS. 


133 


At  other  times  the  inclusions  are  material  which  the  process  of 
crystallization  has  tried  to  eliminate  from  the -crystal.  In  such  a 
case  the  included  material  is  apt  to  be  definitely  arranged  as  in  the 
case  of  the  magnetite  in  mica  from  Chandler's  Hollow,  Del.,  Fig. 

FIG.  256. 


FIG.  257. 


255,  which  is  deposited  on  the  cleavage  planes  of  the  mica  and 
parallel  to  the  mica  prism  of  1 20  degrees.  This  is  also  illustrated 
by  the  regular  grouping  of  the  purer  white  and  less  pure  dark  por- 
tions in  chiastolite  as  shown  in  successive  sections  of  a  crystal  in 
Fig.  256. 

At  times  definite  earlier  formed  minerals  are  in- 
cluded such  as  the  little  curved  crystals  of  chlorite 
(helminth),  Fig.  257,  frequently  found  in  quartz 
and  feldspar,  or  the  fine  hair-like  rutile  in  quartz, 
Fig.  258,  while  at  other  times  the  inclusions  may 
be  microscopic  crystals  (microlites)  or  incipient  crystals  (crystal- 
lites) not  easily  identified. 

FIG.  258. 


Rutile  in  Quartz,  N.  C. 

REGULAR  GROUPING  OF  CRYSTALS. 

The  grouping  of  crystals  is  sometimes  a  character  of  importance. 
Twinning. 

Twinning  has  already  been  described,  pp.  6 1-66. 


134 


DESCRIPTIVE  MIXER ALOG Y. 


Parallel  Growth. 

A  parallel  arrangement  of  all  corresponding  faces  and  edges  is' 
frequently  observed  and  may  be  recognized  by  the  simultaneous 
reflection  of  light  from  all  parallel  faces.  When  the  parallel  crys- 
tals are  minute  they  give  a  velvety  appearance. 


Copper  with  Analcite,  Lake  Superior  ;  Columbia  University. 

Fig.  259  shows  parallel  cubes  of  copper  with  a  crystal  of 
analcite. 

In  certain  instances  the  union  of  many  crystals  in  parallel  posi- 
tion results  in  larger  crystals,  either  of  the  same  form  with  slightly 
curved  faces  as  in  dolomite,  or  of  a  different  form,  as  in  the  forma- 
tion of  octahedral  fluorite  by  the  union  of  cubes. 

Crystals  of  a  mineral  may  be  capped  by  crystals  of  the  same 
mineral  the  structures  strictly  parallel,  but  the  forms  not  necessarily 
alike.  Examples  are': 

Nail  head  Spar.  —  Calcite  rhombohedra  capping  scalenohedra, 
but  with  cleavage  directions  parallel. 

Sceptre  Quartz.  —  Thin  crystals  capped  by  stouter  ones. 


DESCRIPTIVE    TERMS.  135 

Phantom  Effects.  —  An  earlier  stage  of  growth  delicately  out- 
Imed  as  in  quartz,  gypsum  and  fluorite. 

Capped  Quartz.  —  During  the  growth  of  a  crystal  the  planes  at 
ce/tain  intervals  may  be  coated  with  dust  or  fine  lamellae  of  a 
foreign  substance  and  later  the  crystal  may  grow  further.  This 
may  be  repeated  several  times,  forming  thus  parallel  planes  of 
easy  separation,  e.  g.,  capped  quartz. 

Parallel  groupings  sometimes  occur  which  are  less  simple  than 
the  above,  thus  Dana  describes  *  crystallized  copper  occurring  in 
groups  like  Fig.  261,  composed  of  cubes  each  twinned  parallel  to 

FIG.  260.  FIG.  261. 


an  ocUhedral  face  and  these  twins  united  in  parallel  position  so  as 
to  form  branches  at  sixty  degrees  to  each  other  as  shown  in  ideal 
form,  Fig.  260. 

Two  crystals  may  be  united  so  that  a  face  or  an  edge  of  one  are 
parallel  to  a  corresponding  part  of  another  ;  for  example  staurolite 
and  cyanite  with  brachy  pinacoids  parallel ;  prisms  of  rutile  on 
hematite  with  the  prism  edge  of  rutile  perpendicular  to  an  edge  of 
hematite  and  the  prism  face  of  rutile  in  contact  with  basal  plane  of 
hematite. 

IRREGULAR   GROUPING   OF   CRYSTALS. 

Radiating.  —  Diverging  from  a  common  center,  sometimes  form- 
ing nearly  complete  spheres,  as  in  pectolite  from  Paterson,  Fig. 
262.  More  frequently  forming  partial  spheres,  as  shown  in  wavel- 
lite,  Fig.  479. 

*Am.  Journ.  Sti.,  XXXII.,  p.  428,  1886. 


136 


DESCRIPTIVE  MINERALOGY. 


Cockscomb.  —  A  variety  of  radiating,  but  in  which  there  is  a  par- 
tial parallelism  and  the  free  ends  of  the  crystals  form  a  ridge  as  in 
the  specimen  of  Calamine,  Fig.  264. 

FIG.  262.  FIG.  263. 


Pectolite,  Paterson,  N.  J. 


Stibnite,  Felsobanya,  Hungary. 


Rosette  Shaped. — The  crystals  overlapping  like  the  petals  of  a 
rose  as  in  hematite,  Fig.  337. 

FIG.  264. 


Calamine,  Franklin,  N.  J. 

Reticulated.  —  Crossing  like  the  meshes  of  a  net,  as  in  Fig.  263 
of  stibnite. 

Geodc.  —  A  hollow  nodule  lined  with  crystals. 


DESCRIPTIVE    TERMS. 


CRYSTALLINE   AGGREGATES. 


137 


While  the  definite  crystal  is  the  simplest  proof  of  crystalline 
structure,  masses  which  do  not  show  a  single  crystal  face  are 
usually  aggregations  of  crystals  which  have  been  hindered  by  lack 
of  room  or  other  causes  from  assuming  their  characteristic  forms. 
Such  imperfectly  developed  crystals  possess  the  regular  internal 
structure. 

This  is  often  proved  by  the  fact  that  either  the  entire  mass  may  be  split  (cleaved) 
parallel  to  definite  planes  or  different  portions  may  each  be  so  split  parallel  to  its  own 
set  of  planes.  Mineral  masses  which  are  not  opaque  if  examined  by  polarized  light, 
as  explained,  Chapter  XVIII.,  produce  effects  upon  the  light  entirely  different  from 
those  produced  by  a  substance  with  indefinitely  arranged  particles,  and  the  regular 
structure  may  be  proved  by  other  physical  tests. 

INTERNAL  STRUCTURE  OF  AGGREGATES. 

The  internal  structure  of  a  crystalline  aggregate  depends  upon 
the  shape  and  grouping  of  the  imperfect  crystals.      The  important 
terms  used  are  : 
Columnar  Structure. 

The  internal  structure  is  said  to  be  columnar  when  the  imper- 
fectly formed  crystals  are  relatively  long  in  one  direction  and 

FIG.  265. 


Beryl,  Acworth,  N.  H.     N.  V.  State  Museum 


138 


DESCRIPTIVE  MINERALOGY. 
FIG.  266. 


Cyanite,  Litchfield,  Ct.     N.  Y.  State  Museum. 
FIG.  267. 


Fibrous  Serpentine,  Danville,  Quebec.     N.  Y.  State  Museum. 


DESCRIPTIVE    TERMS. 


139 


grouped.  Fig.  265  shows  a  columnar  beryl.  The  columns  may 
be  parallel  or  not. 

Bladed.  —  A  variety  of  columnar  in  which  the  columns  are  flat- 
tened like  a  knife  blade,  as  in  cyanite,  Fig.  266. 

Fibrous.  —  A  variety  of  columnar  in  which  the  columns  are 
slender  threads  or  filaments  due  to  simultaneous  growth  from 
closely  adjacent  supports,  as  in  Fig.  267,  of  the  serpentine  of  Quebec, 
Canada. 

Lamellar  Structure. 

The  structure  is  said  to  be  lamellar  when  the  imperfectly  shaped 

FIG.  268. 


Granular  Magnetite,  Mineville,  N.  Y.     N.  Y.  State  Museum. 

crystals  appear  as  layers  or  plates,  either  straight  or  curved,  as  in 
the  mineral  talc. 

Foliated.  —  A  variety  of  lamellar,  in  which  the  plates  separate 
easily. 

Micaceous.  —  A  variety  of  lamellar  in  which  the  leaves  can  be 
obtained  extremely  thin,  as  in  the  micas. 

Granular  Structure. 

The  structure  is  said  to  be  granular  when  the  imperfectly  shaped 


140 


DESCRIPTIl  TE  MINERAL  OG  Y. 
FIG.  269. 


Kidney  Ore  (Hematite),  Cleator  Moor,  England.     N.  Y.  State  Museum. 
FIG.  270. 


Botryoidal  Prehnite,  West  Paterson,  N.  J.     N.  Y.  State  Museum. 


DESCRIPTIVE    TERMS. 


141 


crystals  appear  as  angular  grains,  which  may  be  coarse  as  in  mag- 
netite, Fig.  268,  or  fine,  as  in  statuary  marble. 

Impalpable.  —  A  variety  of  granular  in  which  the  grains  are 
invisible  to  the  unassisted  eye. 

THE   EXTERNAL   FORM    OF   AGGREGATIONS. 

Many  terms  are  used,  based  upon  a  fancied  resemblance  to  some 
natural  object.  The  more  important  of  these  are  : 

Reniform.  —  With  the  general  shape  of  a  kidney,  as  in  hematite, 
Fig.  269. 

Botryoidal.  —  Having  something  of  the  appearance  of  a  bunch 
of  grapes,  being  made  up  of  several  globular  individuals  close  to- 
gether, as  in  prehnite,  Fig.  270. 

Nodular.  —  Occurring  in  separate  rounded  lumps  or  nodules. 

FJG.  272. 


Limonite,  Hungary. 


Stilbite,  Blomidon,  N.  S. 


Pisolitic.  —  Composed  of  small  rounded  particles  the  size  of  a 
pea,  as  in  bauxite,  Fig.  477. 

Oolitic.  —  Similar  but  smaller  like  fish  roe  as  in  hematite  or 
calcite. 

Stalactitic.  —  In  hanging  cones  or  cylinders  like  icicles,  as  in 
calcite  or  limonite,  Fig.  271. 


142 


DESCRIPTIVE  MINERALOGY. 


Plumose.  —  Like  a  feather,  as  in  a  variety  of  mica,   Fig.    272. 

Sheaf -like.  —  Resembling  a  sheaf  of  wheat,  as  in  Fig.  273,  of 
stilbite. 

Arborescent  or  Dendritic.  —  Branching  like  a  tree  as  in  copper, 
Fig.  390,  or  pyrolusite,  Fig.  274. 

Mossy.  —  Similar  to  dendritic  but  a  more  minute  structure,  as 
the  inclusions  in  moss  agate. 

Coralloidal.  —  Like  coral  in  form  as  in  "  flos  ferri." 

FIG.  274 


Pyrolusite,  Florence,  Italy. 

Amygdaloidal.  —  Almond-shaped  kernels  filling  cavities  made 
by  steam  or  gas,  as  in  thomsonite. 
Wire-like. — As  in  silver,  Fig.  411. 


CHAPTER  XV. 

CHARACTERS  DEPENDENT  ON  COHESION  AND  GENERAL 
CHARACTERS. 

THE  various  resistances  opposed  by  a  crystalline  substance  to 
forces  tending  to  move  or  separate  its  particles  give  rise  to  a  series 
of  characters. 

CLEAVAGE   AND    PARTING. 

Many  crystallized  substances  when  sharply  struck  or  when 
pressed  with  a  knife  edge  split  into  fragments  bounded  by  smooth 
plane  surfaces  which  are  always  parallel  to  faces  of  simple  forms  * 
in  which  the  substance  can  crystallize. 

These  surfaces  are  more  splintery  than  the  true  crystal  faces 
but  the  angles  between  them  are  just  as  exact  as  the  interfacial 
angles. 

When  the  separation  can  be  obtained  with  equal  ease  in  any  part 
of  the  crystal  and  there  is  only  a  mechanical  limit  to  the  thinness 
of  the  resulting  plates,  the  character  is  called  cleavage.  When, 
however,  the  separation  can  be  obtained  only  at  irregular  intervals 
the  character  is  called  parting.  Furthermore,  all  crystals  of  the 
same  substance  show  the  same  cleavage,  whereas  parting  may  be 
obtained  in  one  crystal  and  not  in  another. 

When  cleavage  or  parting  is  obtained  parallel  to  one  face  of  a 
crystal  form  it  will  be  obtained  with  equal  ease  parallel  to  all  faces 
of  the  form.  For  instance,  galenite  cleaves  parallel  to  all  planes 
of  the  cube,  Fig.  275  ;  calcite,  Fig.  276,  in  three  directions  parallel 
to  all  the  faces  of  a  rhombohedron  with  diedral  angles  of  105°  5'  ; 
and  some  crystals  of  hematite  show  parting  planes  parallel  to  all 
the  faces  of  the  rhombohedron. 

Cleavage  may  be  obtained  parallel  to  the  faces  of  two  or  more 
crystal  forms,  for  instance  gypsum  splits  easily  rnto  plates  parallel 
to  the  clino-pinacoid,  these  plates  again  break  parallel  to  the  ortho- 

*  Usually  parallel  to  the  simpler  and  more  frequently  occurring  crystal  forms  ;  in  the 
isometric  system  to  the  cube,  octahedron  or  dodecahedron  ;  in  the  tetragonal  and  hexa- 
gonal systems  to  the  basal  pinacoid,  prism  or  rhombohedron  and  only  rarely  the  pyramid. 
In  the  other  systems  the  arbitrary  selection  of  axes  prevents  a  simple  statement. 

H3 


144 


DESCRIPTIVE  MINERAL  OGY. 


pinacoid  and  to  the  dome  {101}  and  the  final  shape  is  a  rhombic 
plate  with  angles  of  66°. 

Terms  of  Cleavage.  —  Cleavage  is  said  to  be  perfect  or  eminent 
when  obtained  easily,  giving  smooth,  lustrous  surfaces.      Inferior 

Fin.  27; 


Galenite  Cleavage,  Pyrenees,  alter  Lacroix. 

degrees  of  ease  of  cleavage  are  called  distinct,  indistinct  or  imper- 
fect, interrupted,  in  traces,  difficult. 

Manipulation.  —  Directions  of  cleavage  are  often  indicated  by  a 
pearly  lustre  on  faces  parallel  to  the  cleavage  direction,  the  lustre 
being  due  to  repeated  light  reflections  from  cleavage  rifts,  or 

FIG.  276. 


Calcite  Cleavage. 

cracks  may  be  visible.  The  absence  of  indications  is  not  proof 
that  cleavage  cannot  be  obtained,  but  only  that  previous  pressure 
or  shock  have  not  started  the  separation. 


CHARACTERS  DEPENDENT  ON  COHESION.  145 

Cleavage  is  usually  obtained  by  placing  the  edge  of  a  knife  or 
small  chisel  upon  the  mineral  parallel  to  the  supposed  direction  of 
cleavage  and  striking  a  quick,  sharp  blow  upon  it  with  a  hammer. 
In  some  instances  the  cleavage  is  produced  by  heating  and  sud- 
denly plunging  the  mineral  in  cold  water.  Sudden  heat  alone  will 
often  produce  decrepitation  and  with  easily  cleavable  minerals  the 
fragments  will  be  cleavage  forms. 

Frequently  the  cleavage  is  made  apparent  during  the  grinding 
of  a  thin  section. 

Parting  is  a  secondary  character  produced  in  some  instances  and 
not  in  others  as  a  result  of  pressure  after  solidification.  It  takes 
place  along  a  so-called  glide  plane.* 

PERCUSSION  FIGURES. 

If  a  rod  with  a  slightly  rounded  point  is  pressed  against  a  firmly 
supported  plate  of  mica  and  tapped  with  a  light  hammer,  three 
little  cracks  will  form,  radiating  f  from  the  point, 
Fig.  278.     The  most  distinct  of  these  is  always  FIG.  278. 

parallel  to  the  clino-pinacoid,  the  others  at  an 
angle  x  thereto  which  is  53°  to  56°  in  muscovite, 
59°  in  lepidolite,  60°  in  biotite,  61°  to  63°  for 
phlogopite. 

In  the  same  way  on  cube  faces  of  halite  a 
cross  is  developed  with  arms  parallel  to  the  diag- 
onals of  the  face.  On  an  octahedral  face  a 
three-rayed  star  is  developed. 

ELASTICITY. 

Elasticity  is  capable  of  exact  measurement,  but  is  of  little  value 
in  determination  of  minerals.  The  following  terms  are  used  : 

Elastic.  —  A  thin  plate  will  bend  and  then  spring  back  to  its 
original  position  when  the  bending  force  is  removed,  as  in  mica. 

Flexible  or  Pliable. — A  thin  plate  will  bend  without  breaking, 
as  in  foliated  talc. 

*The  artificial  development  of  a  glide  plane  fgbm  in  calcite  is  shown  in  Fig.  277. 

If  the  edge  ad  of  the  larger  angle  is  rested  upon  a  steady  support  and  the  blade  of  a 
knife  pressed  steadily  at  some  point  i  of  the  opposite  edge,  the  portion  of  the  crystal 
between  /  and  c  will  be  slowly  pushed  into  a  new  position  of  equilibrium  as  if  by  rota- 
tion about  fgbm  until  the  new  face  gc'b  and  the  old  face  gcb  make  equal  angles  with 

t  By  pressure  alone,  three  cracks  diagonal  to  these  are  developed. 
10 


146  DESCRIPTIVE  MINERALOGY. 

TENACITY. 

The  following  terms  are  used : 

Brittle.  —  Breaks  to  powder  before  a  knife  or  hammer  and  can- 
not be  shaved  off  in  slices. 

Sectile.- — Small  slices  can  be  shaved  off  which,  however,  crumble 
when  hammered. 

Malleable. — Slices  can  be  shaved  off  which  will  flatten  under 
the  hammer. 

Tough.  —  The  resistance  to  tearing  apart  under  a  strain  or  a 
blow  is  great. 

Ductile. —  Can  be  drawn  into  wire.  Every  ductile  mineral  is 
malleable  and  both  are  sectile. 

The  sectile  minerals  are :  graphite,  bismuth,  copper,  silver, 
gold,  platinum,  chalcocite,  agentite,  molybdenite,  orpiment,  tetra- 
dymite,  senarmontite,  arsenolite,  cerargyrite. 

FRACTURE. 

When  the  surface  obtained  by  breaking  is  not  a  plane  or  a  step- 
like  aggregation  of  planes  it  is  called  a  fracture  and  described  as  : 
Conchoidal,  rounded  and  curved  like  a 
FJG.  279.  shell,  Fig.  279. 

Even,  approximately  plane. 
Uneven,  rough  and  irregular. 
Hackly,  with  jagged  sharp  joints  and 
depressions  as  with  metals. 

Splintery,  with  partially  separated  splin- 
ters or  fibers. 

HARDNESS. 

The  resistance  of  a  smooth  plane  surface  to  abrasion  is  called  its 
hardness,  and  is  commonly  recorded  *  in  terms  of  a  scale  of  ten 
common  minerals  selected  by  Mohs : 

*  In  more  exact  testing  the  crystal  may  be  moved  on  a  little  carriage  under  a  fixed 
vertical  cutting  point  and  the  pressure  determined,  which  is  necessary  to  produce  a  vis- 
ible scratch.  Other  methods  are  planing  or  boring  with  a  diamond  splinter  under  con- 
stant pressure,  and  comparing  the  loss  in  weight  for  a  given  penetration  or  given  num- 
ber of  movements.  The  loss  of  weight  during  grinding  and  the  pressure  necessary  to 
produce  a  permanent  indentation  or  a  crack  have  also  been  used  as  determinants  of 
hardness. 


CHARACTERS  DEPENDENT  ON  COHESION.  147 

1.  Talc,  laminated.  6.  Orthodase,  white  cleavable. 

2.  Gypsum,  crystallized.  7.  Quartz,  transparent. 

3.  Calcitc,  transparent.  8.  Topaz,  transparent. 

4.  Fluorite,  crystalline.  9.  Sapphire,  cleavable. 

5.  Apatite,  transparent.  10.  Diamond. 

A  good  method  is  to  try  the  hardness  of  the  mineral  first  with 
the  finger  nail,  or  a  copper  coin,  then  with  a  pocket  knife,  then  with 
the  indicated  members  of  the  scale. 

I,  2  (2^/2,  barely),  scratched  by  finger  nail. 
3,  scratches  and  is  scratched  by  a  copper  coin. 
3'  4>  5  (S^  barely),  scratched  by  a  knife. 

6.  7,  8,  9,  10,  not  scratched  by  a  knife. 

The  hardness  having  been  approximately  judged  by  the  ease  with 
which  the  knife,  finger  nail  or  copper  coin,  cuts  the  mineral,  is 
checked  by  the  nearest  member  of  the  scale.  If  the  knife  does 
not  scratch  the  specimen  the  harder  members,  6  to  10,  are  used 
successively  until  one  is  found  which  scratches  the  mineral. 

In  testing,  some  inconspicuous  but  smooth  surface  of  the  substance 
is  selected  and  a  sharp  corner  of  the  standard  mineral  is  pressed 
upon  the  surface  and  moved  back  and  forth  several  times  on  the 
same  line  a  short  distance  (y&  inch).  If  the  mineral  is  not  scratched 
it  is  harder  than  the  standard  used,  and  the  next  higher  on  the  scale 
is  tried  in  the  same  way. 

Care  must  be  taken  to  distinguish  between  a  true  scratch  and 
the  production  of  a  "  chalk  "  mark  which  rubs  off.  Altered  sur- 
faces must  be  avoided. 

ETCHING   FIGURES. 

When  a  crystal  or  cleavage  is  attacked  by  any  solvent  the  action 
proceeds  with  different  velocities  in  crystallographically  different 
directions,  and  if  stopped  before  the  solution  has  proceeded  far,  the 
crystal  faces  are  often  pitted  with  little  cavities  of  definite  shape. 

The  absolute  shape  varies  with  many  conditions  ;  time,  tempera- 
ture, solvent,  crystal lographic  orientation  and  chemical  composition. 

The  figures,  whatever  their  shape,  conform  in  symmetry  to  the 
class  to  which  the  crystal  belongs,  and  are  rarely  forms  common 
to  several  classes.  They  are  alike  on  faces  of  the  same  crystal 
form  and  generally  unlike  on  faces  of  different  forms,  and  serve, 
therefore,  as  an  important  means  (perhaps  the  most  important)  for 


148 


DESCRIPTIVE  MINERALOGY. 


determining  the  true  grade  of  symmetry  of  a  crystal  and  also  for 
recognizing  and  distinguishing  faces. 

Fig.  280  shows  the  shape  and  direction  of  the  etchings  upon  a 
cube  of  pyrite.  These  conform  to  the  symmetry  of  the  group  of 
the  diploid,  p.  59.  On  the  other  hand  the  etchings  upon  a  cube 


FIG.  280. 


FIG.  281. 


of  fluorite,   Fig.  281,  show  a  higher  symmetry  corresponding  to 
that  of  the  hexoctahedral  group,  p.  52. 

The  etchings  of  wulfenite,  Fig.  283,  show  the  mineral  to  belong 
to  a  class  of  lower  symmetry  than  that  suggested  by  the  form, 

FIG.  282.  FIG.  283. 


while  the  etchings  of  pyroxene,  Fig.  282,  like  the  form,  are  sym- 
metrical to  one  plane. 

THE  GENERAL  CHARACTERS. 

By  the  general  characters  of  minerals  may  be  understood  those 
characters  which  do  not  appear  to  be  dependent  upon  the  crystal- 
line structure.  The  principal  are  :  specific  gravity,  specific  heat, 
taste,  odor  and  feel. 

SPECIFIC   GRAVITY. 

The  specific  gravity  of  a  substance  is  equal  to  its  weight  divided 
by  the  weight  of  an  equal  volume  of  distilled  water.  The  character 


GENERAL    CHA RA  CTERS. 


149 


is  an  unusually  constant  one,  the  variations  in  varieties  of  the  same 
species  not  being  great  and  even  these  being  due  usually  to  actual 
differences  in  composition. 

Strictly  the  temperature  of  the  water  should  be  4°  C.,  or  if  not  the  result  should  be 
multiplied  by  a  factor  which  is  the  specific  gravity  of  the  water  used.  Generally  :he 
water  is  used  at  the  ordinary  room  temperature  without  correction. 

Pure  material  must  be  selected  free  from  cavities,  and  air  bubbles 
clinging  to  the  surface  must  be  brushed  off  while  the  fragment  is  in 
the  water. 

Substances  soluble  in  water  must  be  determined  in  alcohol, 
benzine  or  other  liquids  in  which  they  are  insoluble,  and  the  result 
multiplied  by  the  specific  gravity  of  the  liquid  used. 

The  specific  gravities  of  the  minerals  considered  in  this  book 
range  from  water  (ice)  0.92,  to  iridosmine  19  to  21. 

Minerals  of  metallic  and  submetallic  luster  are  heavy,  rarely  as 
low  as  4,     The   great  group  of  silicates   range  chiefly  between 
2  and  3.5,   zircon  reaching  4.7.     With  the  ex- 
ception of  the  lead  salts  practically  all  the  other  FlG-  284- 
minerals  here  considered  lie  between  2  and  4. 

Using  the  Chemical  Balance. 

In  using  an  ordinary  chemical  balance  the 
fragment  is  first  weighed  (W)  and  then  sus- 
pended from  one  scale  pan,  by  a  hair  or  very  fine 
platinum  wire,  in  a  glass  of  water  and  reweighed 
(w}.  If  platinum  wire  is  used  it  must  be  counter- 
balanced. 

Sp.  Gr.  =  ^77 

W  —  w 

Using  the  Jolly  Balance. 

In  using  the  Jolly  balance,  Fig.  284,  the  lower 
scale  pan  is  kept  submerged ;  three  readings  are 
made  by  noting  the  heights  at  which  the  index 
on  the  wire  and  its  image  in  the  graduated  mirror 
coincide  with  the  line  of  sight  when  the  spiral 
comes  to  rest. 

A.  Instrument  reading  with  nothing  in  either  scale  pan. 

B.  Reading  with  mineral  in  upper  scale  pan. 

C.  Reading  with  same  fragment  transferred  to  lower  scale  pan. 


150  DESCRIPTIVE  MINERALOGY. 

B-A 
Sp.  Gr.  =£_-£• 

Using  the  Pycnometer  or  Specific  Gravity  Flask. 

Very  porous  minerals  and  powders  are  determined  by  weighing 
in  a  little  glass  bottle  the  stopper  of  which  ends  in  a  fine  tube.  In 
a  later  form  there  are  two  openings,  one,  the  neck,  is  closed  by  a 
ground  stopper  carrying  a  thermometer,  the  other  ends  in  a  capil- 
lary tube. 

In  ordinary  use  the  mineral  is  weighed  (A)  and  the  bottle  full 
of  water  is  also  weighed  (J3).  The  mineral  is  then  inserted  in  the 
bottle  and  displaces  its  bulk  of  water,  and  the  difference  between 
this  weight  (£7)  and  the  sum  of  the  other  two  weights  is  the  weight 
of  the  displaced  water. 


If  special  precautions  *  are  used  this  apparatus  may  be  relied 
upon  to  the  third  decimal  with  one  gram  of  substance. 

Complete  removal  of  air  bubbles  is  secured  by  placing  the  pycnometer  under  an  air 
pump  after  the  fragments  are  covered  with  the  liquid. 

Using  Heavy  Liquids. 

If  a  fragment  of  a  mineral,  which  may  be  very  minute,  is  dropped 
into  a  test-tube  containing  a  liquid  of  higher  specific  gravity  it  will 
float.  If  the  liquid  is  diluted,  the  diluent  being  stirred  in  drop  by 
drop,  there  will  be  one  stage  at  which  the  fragment  if  pushed  down 
will  neither  sink  nor  rise  but  stay  where  pushed. 

The  specific  gravity  of  the  liquid  is  then  determined  either 
roughly  by  dropping  in  fragments  of  material  of  known  specific 
gravity  until  one  is  found  which  just  sinks  and  another  which 
floats,  the  liquid  being  of  a  specific  gravity  between  these  ;  or  for 
more  accurate  determination  the  most  convenient  balance  is  that 
of  Westphal,  Fig.  285.  The  beam  is  graduated  in  tenths  and 
the  weights  A,  B  and  C  are  respectively  unit,  -fa  and  T£¥. 

This  balance  is  so  constructed  that  when  the  thermometer  float 
is  suspended  in  distilled  water  at  15°  C.  a  unit  weight  must  be 
hung  at  the  hook  to  obtain  equilibrium. 

If  then  the  test-tube  is  nearly  filled  with  the  heavy  liquid  and 
weights  added  until  equilibrium  is  secured  the  specific  gravity  is 
known. 

*See  Mier's  Mineralogy  ;  p.  191. 


GENERAL    CHARACTERS. 

For  instance  in  the  figure  the  weights  employed  are  : 
Unit  weight  at  hook,  value  ..............    i.ooo 

Unit  weight  at  sixth  division,  value  .......   0.600 

y1^  weight  at  sixth  division,  value  .........    0.060 

weight  at  ninth  division,  value  ........    0.009 


Specific  gravity  .....................    1.669 


The  Westphal  Balance. 

The  principal  heavy  liquids  are  :  * 

Thoulet  Solution.  —  Mercuric  iodide  and  potassium  iodide,  in  the 
ratio  of  five  parts  to  four  by  weight,  are  heated  with  a  little  water 
until  a  crystalline  scum  forms,  then  filtered.  The  maximum  spe- 
cific gravity  is  nearly  3.2  and  may  be  lowered  by  the  addition  of 
water  to  any  desired  point. 

Klein  Solution.  —  Cadmium  borotungstate  with  a  maximum  spe- 
cific gravity  of  3.6. 

Braun's  Solution. —  Methylene  iodide,  CH2I2,  with  a  maximum 
specific  gravity  of  3.32  which  can  be  lowered  by  the  addition  of 
benzol.  It  darkens  from  exposure  to  light  but  may  be  clarified 
by  shaking  with  a  little  mercury. 

By  addition  of  iodoform  and  iodine  it  may  be  raised  to  a  specific 
gravity  of  3.65. 

*See  Neues  Jahrb.f.  Mm.,  1889,  II.,  185,  for  list  of  solids  which  when  melted 
have  specific  gravity  up  to  5. 


152  DESCRIPTIVE  MINERALOGY. 

Penfidd  Solution.  —  Silver  thallium  nitrate  which  is  liquid  at  75° 
C.,  has  a  maximum  specific  gravity  of  over  4.5  which  can  be  low- 
ered by  the  addition  of  hot  water. 

SPECIFIC    HEAT- 

This  general  property  has  not  been  used  for  the  identification  of 
minerals.  It  may  be  defined  as  the  amount  of  heat  needed  to  raise 
the  temperature  of  a  substance  one  degree,  divided  by  the  amount 
of  heat  necessary  to  raise  the  same  weight  of  water  one  degree. 

The   usual   method   consists  in   heating  the  coarsely  crushed 
mineral,  then  cooling  in  water,  then : 
W  =  weight  of  mineral. 
w  =  weight  of  water. 

T=  degrees  final  temperature  mineral  exceeded  initial. 
/  =  degrees  final  temperature  water  exceeded  initial. 

Specific  Heat  =  — - . 

TASTE. 

Minerals  soluble  in  water  often  have  a  decided  taste : 

Astringent.  — The  taste  of  alum. 

Saline  or  Salty.  —  The  taste  of  common  salt. 

Bitter.  —  The  taste  of  epsom  salts. 

Alkaline.  —  The  taste  of  soda. 

Acid.  —  The  taste  of  sulphuric  acid. 

Cooling.  —  The  taste  of  nitre. 

Pungent.  —  The  taste  of  sal-ammoniac. 

ODOR. 

Odors  are  rarely  obtained  from  minerals,  except  by  setting  free 
some  volatile  constituent.  The  terms  most  used  are  : 

Garlic.  —  The  odor  of  garlic  obtained  by  heating  minerals  con- 
taining arsenic. 

Horseradish.  —  The  odor  of  decayed  horseradish  obtained  from 
minerals  containing  selenium. 

Sulphurous.  —  The  odor  obtained  by  heating  sulphur  or  sul- 
phides. 

Fetid.  —  The  odor  obtained  by  dissolving  sulphides  in  acid. 

Bituminous.  —  The  odor  of  bitumen. 


GENERAL    CHARACTERS.  153 

Argillaceous.  —  Obtained  from  serpentine  and  some  allied  min- 
erals, after  moistening  with  the  breath. 

FEEL. 

Terms  indicating  the  sense  of  touch  are  sometimes  used : 

Smooth.  —  Like  celadonite  or  sepiolite. 

Soapy.  —  Like  talc. 

Harsh  or  Meager.  —  Like  aluminite. 

Cold.  —  Distinguishes  gems  from  glass. 


CHAPTER   XVI. 

THE    OPTICAL   CHARACTERS  WHICH  ARE    OBSERVED    BY 
COMMON  LIGHT. 

LUSTRE. 

THE  lustre  of  a  mineral  is  dependent  upon  its  refractive  power, 
its  transparency  and  its  structure.  It  may  be  called  the  kind  of 
brilliancy  or  shine  of  the  mineral. 

METALLIC  lustre  is  the  lustre  of  metals.  It  is  exhibited  only  by 
opaque  minerals,  and  these,  with  the  exception  of  the  native  metals, 
have  a  black  or  nearly  black  streak. 

NON-METALLIC  lustre  is  exhibited  by  all  transparent  or  trans- 
lucent minerals.  It  may  be  vitreous,  adamantine,  resinous,  pearly, 
silky,  greasy  or  waxy. 

Vitreous.  —  The  lustre  of  a  fracture  surface  of  glass  or  of  a 
quartz  crystal.  Index  of  refraction  n=  1.3  to  1.8. 

Adamantine.  —  The  almost  metallic  lustre  of  the  uncut  diamond, 
zircon  or  cerussite,  exhibited  by  minerals  of  high  index  of  refrac- 
tion, n  =  1.9  to  2.5. 

Resinous.  —  The  lustre  of  resin  or  sphalerite. 

Greasy.  — The  lustre  of  oiled  glass  or  elaeolite.     n  =  1.7  to  1.9. 

Pearly.  —  The  lustre  of  the  mother  of  pearl  or  of  foliated  talc. 
Common  parallel  to  a  very  perfect  cleavage. 

Silky.  —  The  lustre  of  silk  or  of  satin  spar,  due  to  a  fibrous 
structure. 

Dull.  —  Without  lustre  or  shine  of  any  kind.  Kaolin  or  chalk 
are  good  examples. 

The  prefix  sub,  as  sub-metallic,  sub-vitreous,  is  used  to  express 
an  imperfect  lustre  of  the  kind. 

The  words  splendent,  shining,  glistening,  glimmering  and  dull 
are  terms  of  intensity  dependent  on  the  quantity  of  light  reflected. 

Lustre  should,  when  possible,  be  determined  by  a  comparison 
with  minerals  of  known  lustre,  and  should  always  be  observed  on 
a  fresh  or  unaltered  surface. 

The  degree  and  kind  of  lustre  are  always  the  same  on  like  faces 


CHARACTERS    OBSERVED   BY  COMMON  LIGHT.       155 

of  the  crystal,  but  may  be  different  on  unlike  faces,  as  in  apophyllite, 
which  has  pearly  basal  pinacoid  and  vitreous  prism  faces. 

COLOR. 

The  surface  colors  are  of  two  classes. 

1.  Colors  dependent  on  the  chemical  constituents. 

2.  Colors  dependent  on  physical  causes. 

Color  Dependent  on  Chemical  Composition. 

Color  is  one  of  the  least  constant  mineral  characters,  and  varies 
with  different  specimens  of  the  same  species.  It  is  frequently 
changed  by  a  few  hundredths  of  one  per  cent,  of  some  organic  or 
inorganic  substance  dissolved  in  the  mineral,  or  by  larger  amounts 
of  mechanically  included  foreign  material. 

In  describing  color  the  terms  white,  gray,  brown,  black,  blue, 
green,  yellow  and  red  are  used,  with  prefixes,  which  suggest  the 
shade  by  the  color  of  some  familiar  object.  These  need  no  expla- 
nation. 

Color  Due  to  Physical  Causes. 

If  the  observed  surface  color  changes  with  the  direction  in  which 
it  is  viewed  it  is  due  to  interference  of  light. 

Play  or  Change  of  Colors.  —  A  succession  of  colors,  varying  with 
the  direction  the  mineral  is  viewed,  as  in  opal,  labradorite,  or 
diamond. 

Iridescence.  —  Bands  of  prismatic  colors,  either  from  the  interior 
of  a  mineral,  as  from  a  thin  film  of  air  between  cleavages ;  or  ex- 
ternal and  due  to  a  thin  coating  or  alteration. 

Tarnish.  —  A  surface  which  has  been  exposed  to  the  air  or  to 
moisture  is  often  of  different  color  from  the  fresh  fracture. 

Opalescence.  —  A  milky  or  pearly  reflection,  sometimes  an  effect 
of  crystalline  structure,  at  other  times  due  to  fibrous  inclusions. 

Astcrism.  —  A  star  effect  by  reflected  light,  as  in  the  ruby,  or  by 
transmitted  light,  as  in  some  micas,  and  due  to  structure  planes  or 
symmetrically  arranged  inclusions. 

PHOSPHORESCENCE. 

Many  minerals,  after  being  subjected  to  various  outside  influ- 
ences, emit  light"  which  often  persists  for  some  time  after  removal 
of  the  exciting  cause.  Such  emission  of  light  is  known  as 
phosphorescence. 


156  DESCRIPTIVE  MINERALOGY. 

Phosphorescence  may  be  induced  by  ordinary  light,  heat,  fric- 
tion, mechanical  force  or  electrical  stress  but  especially  by  the  action 
of  radium,  polonium  and  actinium  emanations,  by  X-rays  and  by 
ultra-violet  light.  In  a  particular  specimen  it  may  be  induced  by 
only  one  or  by  several  of  the  agencies  named.  Phosphorescence 
is  not  always  a  characteristic  of  species  but  rather  of  the  particular 
specimen  or  of  species  from  a  certain  locality.  On  the  other  hand 
certain  species  are  nearly  always  phosphorescent.  Diamonds  are 
generally  strongly  phosphorescent  under  radium  emanations,  but  the 
degree  of  reaction  varies  with  the  individual  specimen.  They  also 
phosphoresce  under  the  influence  of  polonium,  actinium,  X-rays, 
ultra-violet  rays  and  some  rare  specimens  will  glow  in  the  dark  even 
after  exposure  to  sunlight  or  the  light  of  the  electric  arc.  WilK  mite 
from  Franklin,  New  Jersey,  and  kunzite  are  strongly  phosphor- 
escent under  the  influence  of  radium,  polonium,  actinium  and  X-rays. 
Chlorophane,  a  variety  of  fluorite,  phosphoresces  at  times  by  the 
simple  heat  of  the  hand,  while  fluorite  itself  may  phosphoresce, 
fluoresce  or  do  neither  according  to  the  specimen.  All  minerals  from 
Borax  Lake,  California,  phosphoresce  under  the  influence  of  ultra- 
violet rays,  which  would  seem  to  indicate  some  common  phosphor- 
escent constituent. 

FLUORESCENCE. 

Fluorescence  is  induced  by  much  the  same  agencies  as  phos- 
phorescence, but  the  emitted  light,  which  may  be  white  or  colored, 
persists  only  during  the  action  of  the  exciting  agent.  Colorless 
fluorite  fluoresces  under  the  influence  of  sunlight,  autunite  from 
Mitchell  county,  N.  C.,  and  hyalite  from  San  Luis  Potosi, 
Mexico,  fluoresce  wonderfully  under  the  influence  of  ultra- 
violet light. 

STREAK. 

The  streak  of  a  mineral  is  the  color  of  its  fine  powder.  It  is 
usually  obtained  by  rubbing  the  mineral  on  a  piece  of  hard,  white 
material,  such  as  unglazed  porcelain,  and  brushing  off  the  excess, 
or  it  may  be  obtained  less  perfectly  by  scratching  the  mineral 
with  a  knife  or  file,  or  by  finely  pulverizing  a  fragment  of  the 
specimen. 

The  streak  often  varies  widely  from  the  color  of  the  mass  and  is 
nearly  constant  for  any  species.  When  not  white  it  is  a  character- 
istic very  useful  in  determination. 


CHARACTERS   OBSERVED   BY  COMMON  LIGHT.       157 

TRANSLUCENCY. 

The  translucency  of  a  mineral  is  its  capacity  to  transmit  light. 

A  mineral  is  said  to  be: 

Transparent.  —  When  objects  can  be  seen  through  it  with  clear- 
ness. 

Siibtransparent. — When  objects  can  be  more  or  less  indistinctly 
seen  through  it. 

Translucent. — When  light  passes  through,  as  through  thin  por- 
celain, but  not  enough  to  distinguish  objects. 

Subtranslucent. — When  only  the  thin  edges  show  that  any  light 
passes. 

Opaque.  —  When   no  light  appears   to  pass   even  through  the 

thin  edges. 

REFRACTION. 

When  a  ray  of  light  passes  from  one  substance  into  another  in 
which  its  velocity  is  different,  the  ray  is  bent  or  refracted,  and  the 
amount  of  bending  is  found  to  be  such  that  whatever  the  direction 
of  the  incident  and  refracted  rays  the  ratio  between  the  sines  of  the 
angles  of  incidence  and  refraction  is  constant. 

Light  incident  at  90°  is  not  bent,  and  with  plane  parallel  plates  the  emerging  light 
is  parallel  to  the  incident  light. 

Index  of  Refraction. 

When  light  passes  from  air  into  a  substance,  this  ratio  between 
the  sines  is  called  the  index  of  refraction  of  the  substance,  that  is  : 

sin  i 
n  =    . 
sin  to 

Each  singly  refracting  (isometric)  mineral  will  have  its  character- 
istic index  of  refraction  for  light  of  each  wave-length,  while  for 
doubly  refracting  minerals  there  will  be  two  indices  of  refraction  for 
each  direction  of  transmission. 

Approximate  Determination  of  the  Index  of  Refraction. 

The  index  of  refraction  may  be  approximately  determined  by 
immersing  small  fragments  of  the  mineral  in  a  series  of  liquids 
of  known  refractive  indices.*  If  the  mineral  and  the  liquid  have 
nearly  the  same  indices  the  light  will  go  through  without 


*  The  indices  of  a  few  convenient  liquids  are  :  water,  1.34;  alcohol,  1.36;  glycerine, 
1.41;  olive  oil,  1.47;  nut  oil,  1.50;  clove  oil,  1.54;  aniseed  oil,  1.58;  almond  oil, 
1. 60;  cassia  oil,  1.63;  monobromnapthalene,  1.65;  methylene  iodide,  1.75. 


I58 


DESCRIPTIVE  MINERALOGY. 


noticeable  bending  and  the  outline  and  roughnesses  will  be  invisible, 

but  if  they  differ  materially  the  roughness  will  be  distinctly  visible. 
F.  Krantz,  of  Bonn,  furnishes  *  a  series  of  2  1    liquids  in  glass- 

stoppered  bottles,  the  indices  of  the  liquids  ranging  from  1.447  to 

1.83- 

Measurement  of  Indices  of  Refraction. 

The  Prism  Method.^  —  If  monochromatic  light  is  sent  through 

the  collimator  c,  Fig.  14,  along  a  line  KR,  Fig.  286,  and  enters  at 
one  face  AB  of  a  prism  of  known  angle  X  it  will 
emerge  at  the  other  side  £>C,  deviated  from  its 
course  an  angle  d.  For  one  position  of  the  prism, 
found  by  trial,  this  deviation  d  is  a  minimum  and 
bears  a  definite  relation  to  the  index  of  refraction 
n  and  the  angle  of  the  prism  X  expressed  by 


FIG.  286. 


FIG.  287. 


_ 

--  .         -,      T  -•  • 

sin  \X 

In  hexagonal  and  tetragonal  crystals  the  indices  determined  are 
those  obtained  by  transmission  at  right  angles  to  the  optic  axis. 
Two  images  are  found  which  may  be  distinguished  by  a  nicol's 
prism,  which  transmits  vibrations  parallel  to  its  shorter  diagonal. 
In  orthorhombic,  monoclinic  and  triclinic  crystals  three  indices 
are  determined  corresponding  to  rays  vibrating  parallel  to  the 
acute  and  obtuse  bisectrices  and  a  direction  at  90°  to  both.  At 
least  two  differently  oriented  prisms  are  necessary  to  secure  these  three  indices. 

The  Total  Reflection  Method.  \  —  A  fragment  with  a  natural  or 
polished  plane  face  is  suspended  so  as  to  revolve 
about  a  vertical  axis  in  a  vessel  filled  with  a  liquid 
of  higher  refractive  index  than  the  crystal.      Dif- 
fused   light   is   admitted    from    the  side  and   the 
crystal  is  viewed  by  a  telescope  fixed  at  90°  to 
the  plane  front  of  the  vessel.      For  one  position 
the  field  of  the  telescope  appears  as  in  Fig.  287. 
The  light  is  then  admitted  at  the  opposite  side  and 
the  plate  turned  until  the  field  is  again  half  light,  half  dark.      The 
angle  between  these    two   positions  is   2/,  and  the  index   of  the 
mineral  is  n  =  nl  sin  2,  in  which  «,  is  the  known  index  of  the  liquid. 

In  hexagonal  and  tetragonal  crystals  both  desired  indices  result  from  any  crystal  face. 

*  Price  12  marks. 

f  A.  J.  Moses,  Characters  of  Crystals,  p.  88. 

\  Ibid.  ,  p.  90. 


CHARACTERS   OBSERVED   BY  COMMON  LIGHT.       159 


In  orthorhombic,  monoclinic  and  triclinic  crystals  all  three  indices  can  be  obtained 
from  any  plane  surface  parallel  to  either  bisectrix  or  the  line  at  90°  to  both. 

DOUBLE  REFRACTION. 

If  an  object  is  viewed  through  a  transparent  cleavage  of  calcite,* 
it  will  appear  to  be  double,  as  in  Fig. 
288.     If  such  a  cleavage  is   revolved  FlG  288 

about  a  horizontal  axis  at  90°  to  a  face, 
any  light  ray,  IT,  incident  at  90°,  Fig. 
290,  is  transmitted  in  the  rhomb  as 
two  rays  of  essentially  equal  brightness 
(giving  two  images  of  any  signal),  and 
as  the  rhomb  is  turned  about  the  axis 
one  of  these  remains  fixed  in  position, 
the  other  moves  around  the  first. 

With  single  refraction  and  normal  incidence  only  the  fixed  image 
would  have  been  seen,  hence  this  is  called  the  ordinary  and  the 
movable  image  by  contrast  the  extraordinary. 

That  some  peculiar  change  has  taken  place  other  than  the 
division  of  the  one  ray  into  two  may  be  shown  as  follows  : 


FIG.  289. 


FIG.  290. 


Let  one  of  the  two  rays  be  shut  off  and  the  other  viewed  through 
a  second  calcite  rhomb  similarly  mounted ;  this  ray  is  again  split 
into  two  rays,  an  ordinary  and  an  extraordinary,  but  these  arc  no 
longer  of  equal  brightness,  but  wax  and  wane  in  turn,  the  sum  of 
their  intensities  remaining  constant. 
Planes  of  Vibration. 

The  changes  in  intensity  as  the  second  rhomb  is  turned,  corre- 

*The  property  is  common  to  all  crystals  except  isometric,  but  calcite  possesses  it  in 
a  very  marked  degree.  The  double  image  can  only  be  observed  in  a  few  substances, 
and  the  double  refraction  is  better  proved  by  the  tests  described  later. 


160  DESCRIPTIVE  MINERALOGY. 

spond  exactly  to  the  assumption  that  the  vibrations  of  common 
light  have  been  converted  by  the  first  calcite  into  two  sets  of 
straight-lined  vibrations,  at  right  angles  to  each  other,  the  one 
parallel  to  a  plane  through  ac  and  IT,  Fig.  290,  the  other  at  right 
angles  to  this  plane. 

The  vibrations  of  either  the  extraordinary  or  the  ordinary  ray 
might  be  parallel  to  the  plane  through  ac,  but  it  is  hereafter  as- 
sumed that  the  vibrations  of  the  extraordinary  ray  are  in  a  plane 
through  the  axis  c,  and  those  of  the  ordinary  are  at  right  angles  to 
this  plane. 

On  this  assumption  the  so-called  "  Plane  of  Polarization  "  of  Malus  is  at  right  angles 
to  the  ple.ne  of  vibration  ;  that  is,  the  plane  of  polarization  of  the  ordinary  ray  is  a 
plane  through  the  axis  c,  and  the  plane  of  polarization  of  the  extraordinary  ray  is  at 
right  angles  to  this.  See  Moses's  Characters  of  Crystals,  pp.  98-100. 


CHAPTER  XVIII. 


THE   OPTICAL  CHARACTERS    OBTAINED  WITH    POLARIZED 
LIGHT. 

Nicol's  Prism. 

Plane  polarized  light  is  produced  from  common  light  in  several 
ways,*  the  principal  one  being  transmission  through  a  so-called 
nicol's  prism,  made  from  a  cleavage  of  calcite  with  a  length  about 

twice  its  thickness,  Fig.  291. 

FIG.  291. 

The  two  small  rhombic  faces  at  7 1  °  to  the  edge  are  ground 
away  and  replaced  by  faces  at  68°  to  the  edge.  The  prism  is 
then  cut  through  by  a  plane  at  right  angles  both  to  the  new 
terminal  faces  and  to  the  principal  section.  The  parts  are 
carefully  polished  and  cemented  by  Canada  balsam,  the  index 
of  refraction  of  which  is  1.54  or  about  that  of  the  extraordinary 
ray  bd,  which,  therefore,  passes  through  the  balsam  with  but 
little  change  in  direction  ;  the  ordinary  ray  be,  however,  with 
an  index  of  refraction  of  1.658,  being  incident  at  an  angle 
greater  than  its  critical  angle,  is  totally  reflected. 

The  emerging  light  is  no  longer  common 
light  vibrating  in  constantly  changing  ellipses, 
but  is  plane  polarized,  vibrating  parallel  to  a 
plane  through  the  shorter  diagonal  of  the  face 
of  the  nicol,  as  shown  by  the  arrow. 
Crossed  Nicols. 

The  term  nicol  is  used  to  designate  any  form 
of  polarizer.  If  two  nicols  are  placed  so  that 
the  light  from  one  reaches  the  other,  the  light 
will  go  through  unchanged  if  the  faces  of  the 

*  Other  similar  prisms  exist  and  other  methods  are  : 

Reflection  at  a  particular  angle  of  incidence  (tan  i=n),  the  vibrations  being  at 
right  angles  to  the  plane  of  reflection  (plane  through  incident  and  reflected  ray). 

Refraction  through  a  series  of  parallel  glass  plates,  each  plate  increasing  the  propor- 
tion of  polarized  light.  In  this  case  the  vibrations  are  in  the  plane  of  reflection. 

Double  refraction  and  absorption.  Certain  substances  absorb  one  ray  much  more 
rapidly  than  the  other,  and  a  thickness  can  be  chosen  for  which  one  ray  is  totally 
absorbed,  the  other  being  partially  transmitted  with  vibrations  all  in  one  plane. 
Tourmaline  is  often  used,  as  in  this  mineral  the  ordinary  ray  is  much  the  more  rapidly 
absorbed. 


162 


DESCRIPTIVE  MINERALOGY. 


nicol  are  parallel,  but  as  one  is  rotated  the  percentage  of  light 

emerging  diminishes  and  after  90°  of  rotation,  that  is  with  crossed 

nicols,  none  of  the  light  from 

the   first  nicol    can    penetrate  FIG.  292. 

the  second  and  the  field  must 

be  dark. 

This  may  be  illustrated  by 
two  nicol  prisms  set  rather 
loosely  in  a  hole  bored  in  a 
block  of  wood. 

Polarizing  Microscope. 

A  polarizing  microscope  is 
essentially  a  pair  of  crossed 
nicols  added  to  an  ordinary 
microscope.  Fig.  292  shows 
a  simple  type  of  Fuess.  The 
mirror  sends  parallel  rays 
through  the  lower  nicol,  which 
may  be  raised  or  lowered  by 
the  lever  h.  The  upper  nicol 
N  has  its  vibration  plane  at 
right  angles  to  that  of  the 
lower  nicol  and  may  be 
thrown  in  or  out  by  a  hori- 
zontal motion. 

The  revolving  stage,  the  ob- 
jective, eye  piece  and  methods  of  focussing  are   like  those  of  the 
ordinary'  microscope. 

TESTS    WITH   PARALLEL    RAYS    OF   POLARIZED   LIGHT. 

Depolarization. 

If  a  section  of  any  crystal,  such  as  mica,  is  placed  between  crossed 
nicols,  whether  between  two  nicols  in  a  wooden  stand  or  upon  the 
stage  of  a  polarizing  microscope,  the  dark  field  in  general  becomes 
light ;  whereas  a  plate  of  glass  so  inserted  leaves  the  field  dark. 

The  reason  is  that  all  crystals,  except  the  isometric,  .are  doubly 
refracting.  -The  plate  used  has  opposite  parallel  sides.  1  The  en- 
tering light  is  doubly  refracted  as  in  calcite  and  emerges  as  two 
parallel  rays  vibrating  at  right  angles  to  each  other,  in  directions 
not  generally  parallel  to  the  vibration  directions  of  the  nicols. 


CHARACTERS  WITH  POLARIZED  LIGHT.  163 

Determining  Extinction  Directions  between  Crossed  Nicols. 

The  directions  of  these  vibrations  vary  with  the  section  and  sub- 
stance, but  are  constant  in  parallel  sections  of  different  crystals  of 
the  same  substance.  Hence  their  position  is  a  character  of  value. 

Each  section  has  two  vibration  directions  at  90°  to  each  other, 
which  are  known  as  extinction  directions  because  whenever  either 
is  parallel  to  the  vibration  direction  of  the  lower  nicol  the  light 
goes  through  the  plate  unchanged  in  vibration  direction,  therefore 
still  at  90°  to  the  vibration  of  the  upper  nicol.  The  light  is  there- 
fore unable  to  penetrate  the  upper  nicol  and  the  field  is  dark. 

For  every  90°  this  is  true  but  for  all  other  positions  the  field  is 
illuminated  by  the  components  of  the  rays  which  penetrate  the 
upper  nicol.  This  brightening  is  most  intense  for  positions  diago- 
nal to  the  extinction  directions. 

Manipulation.  —  Place  the  section,  for  instance  a  cleavage  of  mica, 
or  of  gypsum,  on  the  stage  of  the  microscope,  focus  with  the  upper 
nicol  out,  make  some  edge,  cleavage  or  other  outline  coincide  with 
a  cross  hair,  read  the  vernier,  push  in  the  upper  nicol  and  rotate  the 
stage  of  the  microscope  until  the  extinction  direction  is  found  by 
the  darkening*  of  the  field.  Again  read  the  vernier.  The  dif- 
ference between  the  two  readings  is  the  extinction  angle  with  the 
chosen  outline. 

Destructive  Interference,  Monochromatic_Light  and  Crossed  Nicols. 

If  a  ray  of  monochromatic  polarized  light  AB,  Fig.  293,  strikes 
a  crystal  section,  it  is  split  into  two  rays  moving,  for  example, 
in   the  directions  BC  and  BD  and  on   emer- 
gence at  C  and  D  each  ray  travels  parallel  to  FlG-  293- 
the  original  direction,  therefore  to  each  other.  Ill 
These  can  not  interfere.                                                       ij  el  I 

But  some  other  ray  EG  parallel  AB  will  ////f/ 

have  one  resultant  ray  travelling  along  GC  ^^^ 

and  emerging  at  C.     The   rays  EGC,  ABC         I  // 
will  interfere.     That  is  from  each  point  of  the       III 
upper  surface  there  will  emerge  the  ordinary      E  A    'r 
component  of  one  ray  and  the  extraordinary 


*  Maximum  darkness  is  not  as  easily  judged  as  color,  hence  a  closer  determination 
may  be  made  if  the  field  is  made  red  or  violet  by  a  gypsum  or  a  quartz  test-plate,  and 
the  mineral  inserted  so  as  to  only  partly  cover  the  field.  For  the  extinction  positions, 
the  mineral  will  appear  of  the  same  color  as  the  rest  of  the  field. 


1 64 


DESCRIPTIVE  MINERALOGY. 


of  another,  and  these  rays  will  travel  over  the  same  path,  but  their 
vibrations  will  be  at  right  angles  to  each  other. 

Furthermore  one  having  travelled  further  in  the  plate  and  through 
a  different  structure  will  have  been  retarded  a  different  amount  than 
the  other. 

Effect  of  the  Second  Nicol.  —  Each  of  the  two  rays  EGC,  ABC 
will  have  a  component  in  the  direction 
of  vibration  of  the  second  nicol  and 
these  alone  will  be  transmitted.  That. 
is  the  two  rays  with  vibrations  at  90° 
will  become  two  rays  with  parallel 
vibrations.  If  these  vibrations  are  alike 
in  phase  the  intensity  of  the  resultant 
ray  will  be  proportionate  to  the  square 
of  the  sum  of  their  amplitudes,  but  if 
unlike  in  phase  the  intensity  will  be 
proportionate  to  the  square  of  their 
difference. 

There  is  a  shutting  out  of  all  light  by  destructive  interference 
whenever  one  of  the  two  rays  just  described  is  one,  two,  three, 
etc.,  wave-lengths  ahead  of  the  other.* 

For  let  PP,  Fig.  294,  represent  the  entering  vibration  in  direc- 
tion and  intensity,  let  RR  and  DD  represent  the  extinction  direc- 
tions of  the  plate,  and  let  P  represent  the  position  of  vibration  at 
the  instant  of  entering  the  plate. 

Then  r  and  s  will  represent  the  cor-  FIG.  295. 

responding  positions   of  the  component 
vibrations  at  the  same  instant. 

When  one  of  the  two  has  gained,  rela- 
tively, just  a  wave-length  (or  2  or  3,  etc.) 

the  relative  positions  of  the  component  vibrations  are  again  r  and  s. 
The  components  of  Or  and  Os  in  the  vibration  direction  AA  of 
the  second  nicol  are  Oa  and  Ob,  equal  and  opposite.  That  is  the 
light  vibration  is  stopped  and  darkness  results  for  all  positions  of 
the  revolving  stage  of  the  microscope. 

Practical  Confirmation.  —  A  wedge  f  of  doubly  refracting  sub- 

*On  the  contrary  the  field  is  brightest  when  the  faster  ray  is  ahead  $.,  f?.,  f?.,  etc., 
for  now  the  components  on  A  A  are  equal  and  in  the  same  direction. 

|  Very  distinct  lines  can  be  obtained  from  a  little  wedge  of  gypsum  made  by  shaving 
down  a  cleavage  with  a  sharp  knife  or  better  by  rubbing  it  down. 


CHARACTERS  WITH  POLARIZED   LIGHT.  165 

stance  will  show,  in  monochromatic  light,  dark  bands  at  regular 
intervals,  which  vary  with  the  color  of  the  light  used  and  corre- 
spond to  differences  between  the  emerging  rays  of  one,  two,  three, 
etc.,  wave-lengths. 
Interference  Colors  with  White  Light  and  Crossed  Nicols. 

The  difference  between  the  two  rays  or  "  Retardation,"  A,  as 
it  is  called,  depends  upon  three  factors  :  (a)  the  material,  (b)  the 
direction  of  transmission  or  orientation,  (c)  the  thickness  of  the 
section.  These  being  known  A  is  known. 

But  this  retardation  A  may  be  at  the  same  time  approximately 
an  even  multiple  of  the  half  wave-length  of  light  of  one  color  and  an 
odd  multiple  of  the  half  wave-length  of  light  of  another  color.  That 
is,  the  light  of  the  first  color  would  be  very  much  weakened  while 
that  of  the  second  color  would  be  at  nearly  its  full  intensity  and 
instead  of  white  light  there  would  result  a  tint  due  to  a  combina- 
tion of  these  and  other  unequally  dimmed  colors. 
Practical  Example. 

The  effect  can  be  determined  from  A  =  t  (n^  —  ri)  in  which 
A  =  relative  gain  of  faster  ray,  /  =  thickness  of  section,  /  =  wave- 
length =  390  violet,  485  blue,  525  green,  590  yellow,  700=  red 
(all  in  millionths  of  a  millimeter),  nl  —  n  =  difference  in  refractive 
indices  usually  called  "  the  double  refraction." 

For  fixing  these  relations  in  mind  the  following  method  may  be 
used.  A  cleavage  of  mica  or  gypsum  is  tapered  (wedged)  at  the 
edge  after  fastening  to  an  object  glass  with  Canada  balsam  (bal- 
sam in  xylol  is  convenient). 

i  °  The  brightest  interference  color  of  the  cleavage  is  noted  by 
finding  the  extinction  directions  between  crossed  nicols  and  turning 
the  stage  45°. 

2°  By  the  tapering  edge  or  by  use  of  a  quartz  wedge  *  the  order 
of  the  color  is  determined  from  which  a  color  chart  will  give  the 
value  of  A. 

3°  The  thickness  t  may  be  measured  in  a  micrometer  scale. 

4°  The  approximate  strength  of  the  double  refraction  will  result 
by  dividing  the  value  of  A  by  the  thickness  of  the  section  in 
millionths  of  a  millimeter. 

*  By  gradually  inserting  a  thin  wedge  of  quartz  between  the  nicols  so  that  the  cor- 
responding vibration  directions  are  crossed  and  counting  the  number  of  times  the 
original  color  reappears,  if  n  times,  then  the  color  is  a  red,  blue,  green,  etc.,  of  «  -f-  I 
order,  for  which  the  value  may  be  looked  up  in  a  color  chart. 


1 66  DESCRIPTIVE  MINERALOGY. 

5°  This  may  be  checked  by  looking  up  a  recorded  value  or  by 
testing  a  second  section  of  the  same  mineral  of  different  thickness. 

6°  Finally  the  reason  that  the  observed  color  corresponds  to 
the  value  of  A  in  the  chart  may  be  ascertained  by  dividing  A  by 
A  for  each  color,  if  the  quotient  is  i,  2,  3,  4,  etc.,  or  nearly,  that 
color  is  shut  out,  if  it  is  ^,  ^,  |,  or  nearly,  then  that  shade  or 
color  is  in  nearly  its  full  intensity.  If  it  is  intermediate  then  a 
portion  of  the  color  is  extinguished. 

For  instance  let  A  =900  IJL  /u  (millionths  of  a  millimeter). 

QOO 

Violet  - —  =  2.3,  nearer  2\  than  2,  over  \  present. 

39° 

Blue      :-—=  1.85,  nearer  2  than  i£,  over  £  lost. 

4»5 

QOO 

Green    —  -  =  1.72,  nearer  i|  than  2,  about  £  present. 

Yellow  ~ —  =  1.52,  closely  I £,  all  present. 

Red       =  1.3,  nearer  ij  than  I,-  over  £  present. 

The  conclusion,  therefore,  is  that  the  resultant  color  is  composed  of  the  yellow  and 
over  %  of  the  red  and  violet  and  £  or  less  than  \  of  the  blue  and  green. 

Another  factor  has  weight  however.  The  relative  intensity  of  the  colors  in  the 
spectrum  are  very  unequal,  possibly  in  order  named  about  I,  ij,  2,  6,  2.  Bringing 
this  in  we  have  violet  >  \  X  *  =  >  \i  blue  <C  \  X  l\  =  £  approx.,  green  £  X  2  =  l> 
yellow  I  XD  =  6,  red  >  £X2  =  >  *•  That  is,  yellow  greatly  predominates.  The 
red  and  green  balance  and  the  blue  and  violet  slightly  tint  the  yellow. 

The  Vibration  Directions  of  the  Faster  and  Slower  Rays. 

The  extinction  directions  in  the  section  are  found  and  placed  in 
diagonal  position,  a  test  plate  of  some  mineral,  in  which  the  vibra- 
tion directions  have  been  distinguished  and  marked,  is  inserted 
between  the  nicols  (in  a  slot  provided)  with  these  directions  also 
diagonal.  If  the  interference  color  is  thereby  made  higher,  as 
shown  by  the  color  chart,  the  vibration  direction  of  the  faster 
ray  of  the  section  is  parallel  to  the  faster  ray  in  the  marked  plate ; 
if  the  color  is  lowered,  the  corresponding  directions  of  vibration  are 
crossed. 

The  test  plates  most  used  are : 

QUARTER  UNDULATION  MICA  PLATE. — A  thin  sheet  of  mica  on  which  is  marked 
C,  the  vibration  direction  of  the  slower  ray,  which  in  mica  is  the  line  joining  the  optic 
axes.  The  thickness  chosen  corresponds  to  A  =  140^/4  which  is  }  "X  for  a  medium  yel- 
low light  and  yields  a  blue  gray  interference  color. 


CHARACTERS  WITH  POLARIZED  LIGHT.  1 67 

GYPSUM  RED  OF  FIRST  ORDER.  —  A  thin  cleavage  of  gypsum  on  which  is  usually 
marked  a,  the  vibration  direction  of  the  faster  ray.  The  thickness  chosen  corresponds 
to  an  interference  color  of  red  of  first  order,  or  say  A  =  560^,  which  is  essentially  /I 
for  a  medium  yellow. 

DISTINGUISHING  THE  "SYSTEM"    IN  SECTIONS  BETWEEN  CROSSED 
NICOLS    WITH    PARALLEL    POLARIZED    LIGHT. 

The  polarizing  microscope  with  the  cross  hairs  parallel  to  the 
vibration  planes  of  the  polarizer  and  analyzer  and  parallel  faced 
plates,  either  natural  faces  or  cleavages  or  cut  sections,  are  used. 
Isometric  Crystals. 

Homogeneous  isometric  crystals  will  show  no  interference  phe- 
nomena when  viewed  between  crossed  nicols,  that  is  the  field  will 
be  dark  throughout  the  complete  rotation  of  the  stage. 
Tetragonal  and  Hexagonal  Crystals. 

In  all  tetragonal  and  hexagonal  crystals  light  is  transmitted 
in  the  direction  of  the  vertical  axis  without  double  refraction.  In 
all  other  directions  it  is  doubly  refracted,  and  the  amount  of  refrac- 
tion in  any  crystal  is  constant  for  all  directions  equally  inclined  to 
the  vertical  axis. 

The  vertical  axis  c  is  therefore  an  axis  of  optical  isotropy,  and  is 
called  the  OPTIC  AXIS. 

In  sections  at  90°  to  the  vertical  axis  the  field  remains  dark 
throughout  the  entire  rotation  of  the  stage. 

In  all  other  sections  there  is  double  refraction.  The  field  is  dark 
(extinction)  at  intervals  of  90°,  and  brightest  at  positions  diagonal 
to  these. 

The  extinction  directions  are  either  parallel  or  symmetrical  to 
cleavage  cracks  and  crystal  outlines.     With  white  light,  interference 
colors  result  as  described,  p.  165. 
Orthorhombic,  Monoclinic  and  Triclinic  Crystals. 

In  these  crystals  no  true  optic  axis  exists  but  for  light  of  each 
wave-length  and  for  each  temperature  two  directions  of  single  re- 
fraction exist  which  are  called  "optic  axes." 

These  directions  usually  are  nearly  the  same  for  light  of  different 
colors  at  the  same  temperature. 

In  sections  normal  to  an  optic  axis  no  extinction  will  take  place, 
but  with  monochromatic  light  the  field  will  maintain  a  uniform 
brightness  *  during  rotation  of  the  stage  and  with  white  light  there 
may  be  a  color  tint. 

*A.  J.  Moses,  Characters  of  Crystals,  p.  136. 


1 68  DESCRIPTIVE  MINERALOGY. 

In  all  other  sections  the  field  is  dark  every  90°  and  is  illuminated 
for  all  other  positions,  most  brilliantly  in  the  positions  at  45°  to  the 
extinction.  If  white  light  is  used  interference  colors  result  as  de- 
scribed, p.  165. 

In  orthorhombic  crystals  the  extinction  directions  are  always 
parallel  or  symmetrical  to  crystallographic  edges,  cleavage  cracks, 
etc.  In  pinacoidal  faces  they  are  parallel  to  the  crystal  axes. 

In  monoclinic  crystals  the  extinction  directions  are  parallel  or  sym- 
metrical to  edges,  cleavages,  etc.,  only  when  the  section  is  parallel  to 
the  ortho  axis  b,  but  in  all  other  zones  are  unsymmetrical. 

In  triclinic  crystals  all  extinction  directions  are  unsymmetrical. 

TESTS    WITH    CONVERGENT    RAYS    OF   POLARIZED    LIGHT    AND 
CROSSED   NICOLS. 

Producing  the  Convergence. 

If  a  small  lens  is  placed  above  the  lower  nicol  it  will  send  through 

the  crystal-plate  S,  Fig.  296,  rays  converging  towards  its  focus. 

Each  direction  in  which  rays  are  sent  is  traversed 

FIG.  296.        ky  a  minute  bundle   of  parallel  rays,  and  therefore 

!/         for  each  direction  the  same  extinction  and  interference 

-f  pf      phenomena  occur  as  were  described  for  parallel  light. 

,'j  In  other  words  each  direction  yields  a  spot  pl  in 

^     /^S-       the  field,  dark  four  times  and  of  a  specific  color  at  all 
other  times,  and  from  all  these   spots  combined  there 
results  an  "  interference  figure  "  or  picture,  the  shape, 
^J   ^         brightness  and  tints  of  which  depend  upon  the  struc- 
!,'  ture  of  the  plate  for  all  the  directions  traversed  by  the 

~p\ rays. 

Using  the  Microscope  for  Convergent  Light  Effects. 

Convergent  light  tests  are  made  with  the  polarizing 
microscope,  Fig.  292,  by  using  a  high  power  objective  and  placing 
a  small  ^pp^^ent  lens  over  the  lower  nicol.  The  section  is 
focused  with  the  upper  nicol  out  then  ^his  is  pushed  in,  the  lower 
nicol  raised  as  high  as  possible  by  the  4ever  //,  the  eye  piece  re- 
moved and  the  interference  figure  may  be  seen  by  looking  down 
the  tube. 

In  instruments  of  greater  complexity  the  eye  piece  may  be  re- 
tained and  the  interference  figure  made  visible  by  an  additional  lens 
inserted  in  the  microscope  tube. 


CHARACTERS  WITH  POLARIZED  LIGHT. 


169 


FIG.  297. 


The  Norremberg  Polariscope. 

Larger  and  finer  figures  are  obtained  with  the  Norremberg 
polariscope,  Fig.  297 :  e,  c'  are  collecting  lenses  on  each  side  of 
the  polarizer,  above  e'  are  four  plano- 
convex lenses,  n,  forming  the  conden- 
ser and  just  over  these  the  stage  h. 

In  a  separate  tube  system  above  are 
the  objective,  composed  of  four  similar 
plano-convex  lenses  o,  and  at  their 
focal  plane  the  glass  plate  r,  on  which 
a  cross  and  a  scale  are  marked ;  the 
image  there  formed  is  magnified  by  / 
and  viewed  through  the  analyzer  q. 

Isometric  Crystals. 

As  with  parallel  light  any  section 
will  transmit  vibrations  in  any  direction 
with  equal  facility,  the  light  from  the 
polarizer  will  be  transmitted  without 
change  and  will  all  be  shut  out  by  the 
analyzer.  That  is,  the  field  will  remain 
dark  i(.'Jiatcver  the  position  of  the  plate, 
both  in  parallel  and  convergent  polar- 
ized light. 

Tetragonal   and  Hexagonal  (Uniaxial) 

Crystals. 

In  the  absence  of  prepared  sections, 
thin  wulfenite  crystals  and  cleavages 
of  brucite  may  be  used. 

In  sections  at  right  angles  *  to  the 
vertical  axis,  c,  which,  as  explained, 
page  167,  is  an  optic  axis,  there  will 
always  appear  a  dark  cross,  the  arms 
of  which  intersect  in  the  center  of  the 
.  field,  and  remain  parallel  to  the  vibra- 
tion directions  (diagonals)  of  the  nicols  during  rotation  of  the  section. 

*  In  thick  sections  of  quartz  or  cinnabar  the  arms  of  the  cross  do  not  reach  the  center 
and  the  central  circle,  when  white  light  is  used,  is  colored  a  tint  due  to  the  rotation  of 
the  plane  of  polarization. 


I/O 


DESCRIPTIVE  MINERALOGY. 


FIG.  298. 


Any  ray  will  vibrate  either  in  or  at  90°  to  a  plane  through  the  ray  and  the  optic  axis. 
Hence  the  rays  transmitted  parallel  to  the  vibration  planes  of  the  crossed  nicols  have 
their  vibrations  in  these  planes  and  are  totally  extinguished.  As  the  stage  is  rotated 
successive  rays  come  into  these  positions  maintaining  the  same  effect. 

Uniaxial  Crystals  with  White  Light. 

The  interference  figure,  if  colored 
at  all,  will  show  colored  circles 
around  the  center  of  the  cross. 

For  the  phase  difference  increases 
as  the  angle  of  the  rays  with  the 
optic  axis  increases,  and  as  ALL 
RAYS  at  any  given  angle  have  the 
same  phase  difference,  the  colors 
which  result  are  in  circles. 

The  reasons  are  as  for  parallel  light.  For 
light  of  each  wave-length  destructive  interfer- 
ence takes  place  at  those  points  at  which  the 

"Retardation  A"  is  equal  to  one,  two  or  three,  etc.,  wave-lengths  of  the  light,  p. 
164.  Therefore,  that  particular  color  is  extinguished  in  circles  around  the  center  of  the 
cross  at  distances  apart  varying  with  the  crystal  and  the  thickness  of  the  crystal  section. 

In  sections  of  the  same  mineral  the  thicker  the  section  the  closer 
the  rings,  while  in  sections  of  different  minerals  but  equal  thickness 
the  greater  the  value  of  the  double  refraction,  (;/'  —  n\  p.  165,  the 
closer  the  rings. 
Optically  -f  and  —  Uniaxial  Crystals. 

If  the  quarter  undulation  mica  plate,  p.  1 66,  is  inserted  between 
the  nicols  and  above  the  crystal  section  it  will  break  up  the  interfer- 


ence  figure  differently  in  different  crystals.  The  color  circles  will 
become  four  quadrants  and  instead  of  the  black  center  there  will 
be  two  black  dots.  The  effects  in  so-called  "  positive  "  and  "nega- 
tive" crystals  are  shown  in  Figs.  299  and  300.  The  corresponding 


CHARACTERS  WITH  POLARIZED  LIGHT. 


171 


signs  -f  and  —  are  suggested  by  the  relative  positions  of  the  dark 
flecks  and  the  arrow  showing  the  direction  c  of  the  test  plate. 

When  no  colored  rings  are  to  be  seen  it  is  more  convenient  to 
insert  a  gypsum  red  of  first  order  plate,  p.  167,  with  its  direction 
a  in  diagonal  position,  the  effect  being  that  "blue  quadrants"  cor- 
respond in  position  to  the  black  flecks.  This  determination  must 
be  made  in  white  light. 
In  Orthorhombic,  Monoclinic  and  Triclinic  (Biaxial)  Crystals. 

In  the  absence  of  prepared  sections,  cleavages  of  mica  and  topaz 
yield  good  figures. 

In  orthorhombic,  monoclinic  and  triclinic  crystals  no  direction 
exists  which  corresponds  to  the  optic  axis  of  hexagonal  and  tetrag- 
onal crystals,  but  at  any  given  temperature  there  are  two  direc- 
tions for  each  color  of  light  which  are  directions  of  single  refrac- 
tion. These  directions  are  therefore  to  this  extent  like  the  optic 
axis  of  hexagonal  and  tetragonal  crystals  and  give  the  name  "  Bi- 
axial "  to  the  crystals.  The  line  which  bisects  the  acute  angle 
between  these  "  axes  "  is  called  the  Acute  Bisectrix*  or  Bxa. 

Sections  at  90°  to  Acute  Bisectrix  Between  Crossed  Nicols  in  Con- 
vergent White  Polarized  Light. 

The  crystal  sections  most  frequently  studied  are  cut  at  90°  to 
the  Bxa  for  yellow  light  at  ordinary  room  temperature.  In  such 
sections  the  points  of  emergence  of  the  optic  axes  are  black,  f  and 

FIG.  301. 


when  the  line  connecting  these  is  parallel  to  the  diagonals  of  the 
nicols,  there  is  a  sharp  dark  band,  Fig.  301,  joining  the  axes  and 
another  somewhat  thicker,  lighter  band  at  right  angles  to  the  first 

*  Similarly  the  line  bisecting  the  obtuse  angle  between  the  axes  is  known  as  the 
Obtuse  Bisectrix,  Bx0. 

f  This  assumes  the  optic  axes  for  different  colors  to  emerge  approximately  at  the 
same  points.  If  there  is  notable  "dispersion  "  the  black  bands  and  hyperbolae  may  be 
rainbow  hued  as  with  titanite. 


1/2  DESCRIPTIVE  MINERALOGY. 

and  midway  between  the  axes.      These  lines  are  due  to  the  shut- 
ting out  of  rays  vibrating  parallel  to  the  nicols. 

If  the  section  is  turned,  other  rays  vibrate  parallel  to  the  nicols  and 
the  straight  dark  lines  seem  to  dissolve  into  hyperbolae,  Fig.  302, 
the  branches  of  which  rotate  in  the  opposite  direction  to  the  rota- 
tion of  the  stage.  The  convex  side  of  each  is  always  toward  the 

other  branch. 

Color  Rings.  —  If  any  color  is 
shown  it  is  in  curves  made  up  of 
the  points  of  emergence  of  all  rays 
with  the  same  phase  difference. 
These  curves  are  not  circles. 

That  is  for  each  color  the  points  corre- 
sponding to  A//  =  I  will  together  form  a  ring 
around  each  axis  and  similarly  for  values  of 
2,  3,  4,  etc.,  until  the  pair  corresponding 
most  nearly  to  the  value  A/A  for  the  center  of 
the  field  unite  at  or  near  the  center  to  a 
cross  loop  or  figure  eight  around  both  axes 
and  subsequent  rings  form  lemniscates  around 
this  as  in  Fig.  302. 

There  is  no  change  in  shape  during  rotation  of  the  stage.  If  A// 
for  the  center  is  less  than  unity  even  the  first  ring  will  surround 
both  axes. 

With  sections  of  the  same  mineral  the  thicker  the  section  the 
closer  together  are  the  rings,  and  with  sections  of  different  minerals, 
but  equal  thickness,  the  greater  the  "  double  refraction,"  p.  165,  the 
closer  together  the  rings. 
Optically  +  and  —  Biaxial  Crystals. 

If  the  distance  between  the  axial  points  in  the  interference  figure 
obtained  from  a  section  at  90°  to  the  acute  bisectrix,*  is  small,  the 
quarter  undulation  mica  plate  may  be  used  as  described,  p.  170,  for 
uniaxial  crystals. 

If  the  distance  between  the  axial  points  is  large,  the  interference 
figure  is  placed  with  the  line  joining  the  axial  points  in  diagonal 
position,  as  in  Fig.  302,  and  the  quartz  wedge,  p.  165,  is  gradually 
inserted  with  the  direction  c  parallel  to  this  line.  If  the  crystal  is 
positive  the  rings  around  each  axis  will  expand,  moving  toward  the 

*  To  determine  the  acute  bisectrix  it  may  be  necessary  to  first  measure  the  axial 
angle.  Ordinarily  the  interference  figure  in  a  section  normal  to  the  obtuse  bisectrix 
will  not  come  within  the  limits  of  the  field. 


CHARACTERS  WITH  POLARIZED   LIGHT. 


173 


center  and  corresponding  rings  will  merge  in  one  curve.  If  the 
crystal  is  negative  the  rings  will  contract  and  increase  in  number, 
the  change  increasing  with  the  thickness  of  wedge  interposed. 

In  a  section  normal  to  the  obtuse  bisectrix  these  results  are  all 
reversed. 

Determination  of  the  Angle  Between  the  Optic  Axes. 

The  axial  angle  may  be  determined  approximately  in  any  polar- 
iscope,  or  suitably  equipped  microscope,  by  measuring  the  distance 
d  from  the  center  to  either  hyperbola  with  a  micrometer  eye-piece, 
or  better  by  averaging  the  distances  to  both.  Then  sin  E  =  dj  C, 

FIG.  303. 


or  sin  V=  dj  ftC,  in  which  C  is  a  constant  for  the  same  system  of 
lenses  and  is  determined  once  for  all  by  using  a  crystal  of  known 
axial  angle. 


For  instance  if  in  a  mica  2.E  r—  91°  jc/  and  d  = 
C=  <//sin  E  =  57.78  for  that  combination  of  lenses. 


divisions  on  the  scale,  then 


The  axial  angle  is  2  V,  and  2E  is  the  so-called  apparent  angle. 
A  more  exact  measurement  may  be  made  by  placing  at  P,  Fig. 


1/4  DESCRIPTIVE  MINERALOGY. 

303,  between  the  lenses  of  a  horizontal  polariscope*  a  section 
cut  at  90°  to  the  acute  bisectrix.  The  vibration  directions  of  the 
nicols  of  the  polariscope  are  crossed  at  45°  to  the  horizon,  so  that 
when  the  line  connecting  the  axial  points  is  horizontal  the  inter- 
ference figure  shows  the  hyperbola  and  not  the  cross.  The  section 
is  centered  so  that  a  line  in  it  is  the  axis  of  revolution ;  and  so  that 
the  axial  points  of  the  interference  figure  remain  on  the  horizontal 
cross  hair  during  revolution. 

The  crystal  is  then  revolved  by  the  horizontal  circle  until  the 
two  arms  of  the  interference  hyperbola  are  successively  made  tan- 
gent to  the  vertical  cross-hair,  the  positions  being  read  on  the  circle. 
The  difference  between  the  two  readings  is  the  apparent  angle  2E, 
and  this  is  frequently  the  angle  recorded.  It  is  always  larger  than 
the  true  angle,  2  V. 

To  find  the  True  Angle  from  the  Apparent  Angle. 

A  second  measurement  may  be  made  of  the  apparent  angle  in  a 
plate  normal  to  the  obtuse  bisectrix.  Denoting  this  by  2FJ  the 

sin  E 

relation  is  tan  V=  -. — ~  • 
sin  E' 

Optical  Distinctions  Between  Orthorhombic,  Monoclinic  and  Triclinic 

Crystals  with  Convergent  Light. 

The  interference  figure,  in  shape  and  in  distribution  of  color,  is 
symmetrical  to  the  planes  and  axes  of  symmetry  of  the  system. 
Hence  the  orthorhombic  figures  are  more  symmetrical  than  the 
monoclinic  and  these  again  than  the  triclinic. 

In  orthorhombic  crystals  the  interference  figure  obtained  in  sections 
parallel  to  two  of  the  three  pinacoids  will  be  like  Fig.  302,  and  if 
the  figures  so  obtained  are  viewed  in  white  light  the  color  dis- 
tribution will  be  symmetrical  to  the  line  joining  the  optic  axes,  to 
the  line  through  the  center  at  right  angles  thereto  and  to  the  central 
point. 

In  monoclinic  crystals  an  interference  figure  similar  to  Fig.  302 
will  be  found  either  in  the  section  parallel  to  the  clino-pinacoid  or 

*  Fig.  303  shows  the  Universal  Apparatus  of  Fuess.  The  centering  device  is  pre- 
cisely that  described  under  the  goniometer,  p.  9.  If  inverted  it  forms  with  the  tele- 
scopes F^  and  F  a  goniometer. 

When  used  for  axial  measurements,  the  crystal  stand  is  replaced  by  the  pincers  P 
which  clip  the  crystal  plate.  The  optical  portion  inserted  at  A  and  Al  is  the  same 
Norremberg  arrangement  of  nicols  and  lenses  which  is  shown  in  Fig.  297,  but  turned  so 
that  the  vibration  directions  of  the  nicols  cross  at  45°  to  the  horizon. 


CHARACTERS  WITH  POLARIZED  LIGHT.  175 

in  one  of  two  sections  normal  to  this.  In  white  light  the  distribu- 
tion of  color  of  this  figure  will  never  be  symmetrical  to  two  lines  as 
in  the  orthorhombic,  but  will  be  symmetrical  either  to  the  line  join- 
ing the  axial  points,  or  to  the  line  normal  to  these,  or  to  the  cen- 
tral point. 

/;/  triclinic  crystals  in  white  light,  the  distribution  of  color  in  the 
interference  figure  is  without  symmetry  to  any  line  or  point. 

ABSORPTION    AND    PLEOCHROISM. 

Light  during  transmission  through  a  crystal  is  in  part  absorbed 
and  in  most  instances  diminishes  steadily  in  intensity  as  the  dis- 
tance traversed  increases. 

With  white  light  the  different  component  colors  are  often  ab- 
sorbed at  different  rates,  giving  color  tints  due  to  the  combination 
of  the  remaining  colors. 

In  Isometric  Crystals. 

A  section  of  any  given  thickness  will  transmit  the  same  color- 
tint  whatever  the  direction  in  which  the  crystal  may  be  cut. 

In  Doubly  Refracting  Crystals. 

In  all  doubly  refracting  crystals  the  ordinary  and  extraordinary 
rays  transmitted  in  any  given  direction  may  be  differently  absorbed. 

Thus,  if  an  apparently  transparent  prism  of  tourmaline  is  placed 
on  the  stage  of  a  polarizing  microscope  with  the  upper  nicol  out 
and  the  stage  is  turned,  the  prism  will  darken  and  will  become 
opaque  when  its  length  is  at  90°  to  the  vibration  direction  of  the 
lower  nicol,  but  will  be  transparent  when  the  length  is  parallel  to 
this  vibration. 

In  other  instances  colors  result  from  partial  absorption  of  certain 
tints.  As  before  the  absorption  varies  with  the  vibration  direction, 
so  that,  again  using  a  polarizing  microscope  with  the  analyzer  out, 
the  color  varies  as  the  stage  is  turned  and  the  maximum  color  differ- 
ences are  obtained  when  the  extinction  directions  of  the  crystal  sec- 
tion coincide  with  the  vibration  plane  of  the  polarizer. 

For  instance,  in  iolite,  transmission  parallel  the  c  axis  gives  a 
gray  and  a  blue,  transmission  parallel  the  ~b  axis  gives  a  gray 
and  a  yellow,  and  transmission  parallel  the  d  axis  gives  a  blue 
and  a  yellow.  In  other  words  the  light  vibrating  parallel  a  is 
gray,  parallel  ~b  is  blue,  parallel  c  is  yellow. 


DESCRIPTIVE  MINERAL  OGY. 


The  colors  of  the  ordinary  and  extraordinary  rays  may  be  con- 
trasted side  by  side  by  means  of  a  "  dichroscope,"  consisting,  Fig. 
304,  of  a  rhomb  of  calcite,  in  which  ab  and  cd  are  the  short  diag- 

FIG.  304. 


onals  of  opposite  faces.  To  these  faces  glass  wedges  aeb,  dfc,  are 
cemented  and  the  whole  encased.  The  section  is  placed  at  P  and 
turned  until  the  two  images  show  their  maximum  difference  in 
color,  the  light  from  the  substance  passes  through  a  rectangular 
orifice,  a  double  colored  image  of  which  is  seen  by  the  eye  at  E. 


CHAPTER  XVIII. 

THE  THERMAL,  MAGNETIC  AND  ELECTRICAL  CHARACTERS. 
THE    THERMAL    CHARACTERS. 

Transmission  of  Heat  Rays. 

HEAT  rays  may  be  reflected,  refracted,  doubly  refracted,  polar- 
ized and  absorbed,  and  it  is  possible,  though  difficult,  to  determine 
a  series  of  thermal  constants  for  crystals. 
Conductivity. 

The  rapidity  with  which  heat  is  conducted  in  different  directions 
in  a  crystal  is  in  accordance  with  its  symmetry.  This  may  be 
shown  on  any  face  or  cleavage  surface  as  follows : 

(a)  The  surface  is  breathed  upon,  quickly  touched  by  a  very  hot  wire,  dusted  with 
lycopodium  powder,  turned  upside  down  and  tapped  carefully.  The  powder  falls  from 
where  the  moisture  film  has  evaporated,  but  adheres  elsewhere,  giving  a  sharply  out- 
lined figure.  The  entire  operation  should  take  less  than  three  seconds. 

(l>)  The  surface  is  coated  with  a  mixture  of  three  parts  elaidic  acid  and  one  part 
wax,  brought  into  contact  with  a  hot  wire,  and  the  temperature  maintained  until  the  wax 
has  melted  around  the  wire.  The  boundary  of  the  melted  patch  is  visible,  after  cool- 
ing, as  a  ridge. 

A  circle  indicates  either  an  isometric  crystal  or  a  basal  section 
of  a  hexagonal  or  tetragonal  crystal.     All  other  sections  yield 
ellipses  varying  in  eccentricity  and  in  position  of  axes. 
Expansion. 

When  a  crystal  is  uniformly  heated,  directions  crystallographic- 
ally  alike  expand  in  the  same  proportion,  but  directions  unlike 
do  not. 

The  expansion  may  be  accurately  measured  for  any  direction 
but  the  methods  involve  apparatus  of  great  precision  and  cost. 
Change  of  Crystal  Angles  Produced  by  Expansion. 

An  isometric  crystal  uniformly  heated  expands  without  change 
of  angles.  In  all  other  systems  the  expansion  varies  with  the 
direction  and  certain  angles  are  changed  (sometimes  several  min- 
utes for  1 00°  temperature  alteration.  For  instance,  the  calcite 
rhombohedron  angle  is  lessened  8'  37")-  The  zone  relations  and 
indices  are  never  changed. 

12  177 


178  DESCRIPTIVE  MINERALOGY. 

These  changes  may  be  measured  with  accurate  goniometers  and 
the  relative  expansions  calculated. 
Change  of  Optical  Characters  Produced  by  Expansion. 

The  expansion  of  a  crystal  changes  the  indices  of  refraction  for 
different  directions.  With  isometric  crystals  the  index  may  become 
either  larger  or  smaller.  With  tetragonal  and  hexagonal  crystals 
the  principal  indices  of  refraction  may  alter  unequally.  The  inter- 
ference figure  will  also  alter  and  for  a  particular  temperature  will 
disappear. 

In  orthorhombic,  monoclinic  and  triclinic  crystals  the  interference 
figure  may  undergo  even  more  striking  changes.  For  instance, 
Fig.  305  represents  such  a  series  in  gypsum  with  yellow  light 

FIG.  305. 


for  which  at  20°  C.  the  axial  angle  is  92°  (Fig.  a),  at  100°  C.  is 
reduced  to  51°  (Fig.  <£),  at  1 34°  C.  is  zero  (Fig.  c),  and  for  still 
higher  temperatures  the  optic  axes  pass  into  a  plane  at  right 
angles  to  their  former  position  (Figs,  d  and  c). 

THE   MAGNETIC   CHARACTERS. 

Magnetism.  —  A  few  iron-bearing  minerals  attract  the  magnetic 
needle  or  are  attracted   by  a  steel  magnet.     Of  these  minerals, 
magnetite,  pyrrhotite  and  platinum  will  themselves  occasionally 
act  as  magnets. 
Para-  and  Diamagnetism. 

Any  substances  will  be  either  attracted  or  repelled  in  some 
degree  in  the  field  of  a  strong  electromagnet. 

If  a  rod  of  the  substance  is  suspended  by  a  fiber  so  as  to  swing  horizontally  between 
the  poles  of  an  electromagnet,  the  rod  is  paramagnetic,  if  pulled  into  "  ajci'af"  posi- 
tion with  its  ends  as  near  the  poles  of  the  magnet  as  possible,  and,  is  diamagnetic,  if 
pushed  into  an  "equatorial"  position  with  its  ends  as  far  from  the  magnetic  poles  as 
possible. 

Crystals  are  more  strongly  magnetized  in  certain  directions  than  in  others. 

ELECTRICAL   CHARACTERS. 

Frictional  Electricity. 

All  minerals  are  electrified  by  friction  but  the  +  or  —  character 
may  vary  in  varieties  of  a  species  and  even  in  the  same  specimen. 


MAGNETIC  AND   ELECTRICAL    CHARACTERS.          179 

If  a  light,  horizontally-balanced  needle  terminating  in  small  balls,  is  electrified, 
either  positively  by  bringing  near  a  rod  of  electrified  sealing  wax,  or  negatively  by 
touching  with  the  rod,  an  electrified  mineral  will  attract  or  repel  the  needle  according 
as  it  has  opposite  or  similar  electricity. 

Electrical  Conductivity. 

All  minerals  conduct,  but  practically,  conductivity  is  limited  to 
the  metals,  some  metalloids,  most  sulphides,  tellurides,  selenides, 
bismuthides,  arsenides  and  antimonides,  some  of  the  oxides,  and, 
at  higher  temperature,  a  few  haloids. 

If  a  rod  is  introduced  into  a  weak  current,  the  strength  of  which  is  varied  by  resist- 
ances and  the  deviation  observed  in  a  galvanometer,  the  results  will  vary  for  different 
minerals  between  very  wide  limits  dependent  upon  the  constitution  of  the  chemical 
molecule  more  than  upon  the  crystalline  structure. 

Thermo-electricity. 

If  two  conducting  minerals  are  made  part  of  a  metallic  circuit, 
heating  or  cooling  the  junction  will  develop  *  an  electric  current, 
the  strength  of  which  will  depend  upon  the  change  of  temperature 
and  upon  the  minerals  used.  » 

Among  metals  a  series  based  upon  the  strength  and  direction  of  the  current  extends 
from  bismuth  at  the  positive  end  to  selenium  at  the  negative  end.  The  position  of 
minerals  in  the  series  may  be  practically  determined. 

A  current  is  developed  by  coupling  two  rods  cut  from  different 
directions  in  the  same  crystal  and  in  the  case  of  pyrite  opposite 
currents  are  produced  by  coupling  copper  with  the  +  or  —  pyrito- 
hedron. 

Pyroelectricity  and  Piezoelectricity. 

Poorly  conducting  crystals  which  have  not  a  center  of  symmetry 
if  altered  in  volume  either  by  a  temperature  change  or  by  pressure 
will  frequently  accumulate  positive  and  negative  charges  of  elec- 
tricity at  different  points. 

PYROELECTRICITY.  —  Usually  the  crystal  is  heated  f  in  an  air- 
bath  to  a  uniform  temperature,  then  drawn  quickly  once  or  twice 
through  an  alcohol  flame  and  allowed  to  cool.  During  the  cooling 
of  the  crystal  positive  charges  collect  at  the  so-called  antilogue 
poles,  and  the  negative  charges  at  the  analogue  poles,  \  and  may 
be  distinguished  by  their  effect  on  other  electrified  bodies.  For 


*  The  possible  cause  of  currents  in  metallic  veins. 

f  If  heating  injures  the  crystal  it  may  be  cooled  from  room  temperature  by  a  freezing 
mixture. 

t  With  rising  temperature  these  are  reversed. 


ISO  DESCRIPTIVE  MINERALOGY. 

instance,  a  cat's  hair  rubbed  between  the  ringers  becomes  positively 
electrified  and  is  attracted  by  the  analogue  pole  and  repelled  by 
the  antilogue  pole. 

Kundf s  Method.  —  The  positive  and  negative  poles  may  be  dis- 
tinguished by  blowing  upon  the  cooling  crystal  a  fine  well  dried  * 
mixture  of  equal  parts  of  powdered  sulphur  and  red  oxide  of  lead. 
The  nozzle  of  the  bellows  is  covered  by  a  fine  muslin  net.  By 
mutual  friction  in  passing  through  the  sieve,  the  sulphur  is  nega- 
tively electrified  and  is  attracted  by  the  antilogue  poles  coloring  them 
yellow  while  the  minium  is  positively  electrified  and  is  caught  by 
the  analogue  poles,  coloring  them  red.  The  dust  should  fall  evenly 
and  the  bellows  be  held  far  enough  away  to  prevent  direct  action 
of  the  blast. 

Figs.  306,  307  and  308  show  crystals  of  tourmaline,  calamine  and 
boracite  respectively,  the  darker  dotted  portions  representing  the 


FIG.  306.  FIG.  307.  FIG.  308. 


accumulation  of  minium  at  the  analogue  poles  and  the  hatched 
portions  the  accumulations  of  sulphur  at  the  antilogue  poles. 

If  the  crystals  had  been  dusted  during  the  heating  the  analogue 
poles  would  have  been  coated  with  sulphur  and  the  antilogue  poles 
with  minium. 

In  PIEZOELECTRICITY  the  charges  are  developed  by  pressure,  for 
instance,  calcite  pressed  between  the  fingers  becomes  positively 
electrified,  tourmaline  compressed  in  the  direction  of  the  vertical 
axis  develops  a  positive  charge  at  the  antilogue  end  and  a  negative 
charge  at  the  analogue  end  or  precisely  the  charges  which  would 
result  from  cooling  a  heated  crystal. 

The  charges  are  detected  in  the  same  way  as  the  pyroelectric 
charges. 

*  Dry  over  H2SO4  in  a  vessel  from  which  the  air  has  been  partially  exhausted. 


CHAPTER   XIX. 


CHEMICAL    COMPOSITION    AND    REACTIONS. 

As  has  already  been  stated,  minerals  are  distinguished  from 
rocks  by  something  of  regularity  in  their  chemical  structure.  Their 
chemical  composition  is  their  most  important  characteristic  whether 
for  identification  or  classification.  The  only  clear  conception  of  the 
relationship  between  minerals  is  based  upon  the  elements  of  which 
they  are  composed,  but  while  they  may  be  best  considered  as 
derived  from  definite  chemical  types  they  are  very  far  from  being 
of  definite  and  invariable  composition  and  it  is  often  difficult  to 
represent  the  results  of  analysis  by  an  exact  formula.  This  is 
readily  understood  when  the  laws  of  isomorphism  and  the  con- 
ditions underlying  the  formation  of  minerals  are  studied. 

ISOMORPHISM. 

Certain  chemical  substances  having  a  distinct  similarity  in  their 
molecules  and  presenting  a  close  resemblance  in  their  reactions 
crystallize  in  forms  which  in  the  regular  system  are  identical  and 
in  the  other  systems  are  so  closely  related  as  to  require,  at  times, 
special  care  in  angle  measurement  to  recognize  any  difference. 
Such  substances  are  said  to  be  isomorphous  when  they  can  replace 
each  other  in  the  same  crystal  or  crystallize  together  to  form 
homogeneous  mixed  crystals. 

Compounds  which  are  isomorphous  generally  have  the  same 
number  of  atoms  in  their  molecules  and  close  similarity  in  their 
structure.  Replacing  isomorphous  elements  usually  have  the  same 
valency  and  are  closely  related  chemically. 

The  carbonates 

Calcite,  CaC03 
Aragomte,  CaCO3 


Strontianite,  SrCO3  and         Smithsonit     ZnCO 

Witherite,  BaCO3  Magnesite,  MgCO, 

Cerrussite,  PbCO3  Rhodochrosite,  MnCO3 

iorm  two  characteristic  isomorphous  groups,  the  first  orthorhombic 
and  the  second  rhombohedral. 

181 


1 82  DESCRIPTIVE  MINERALOGY. 

Such  isomorplwus  compounds  are  capable  of  mixing  in  varying 
proportions  to  form  homogeneous  crystals,  as  Mitscherlich  has  shown 
and  they  cannot,  therefore,  be  separated  by  ordinary  crystallization, 
as  the  analogous  compounds  crystallize  together,  and  the  crystals 
formed  show  by  analysis  the  most  varied  quantitative  proportions 
of  the  isomorphous  substances  originally  present.  Not  only  may 
mixed  crystals  be  formed  by  the  intermingling  of  different  mem- 
bers of  isomorphous  groups  but  individuals  may  combine  in  molec- 
ular proportions  to  form  double  salts  like  dolomite,  CaCO3,  MgCO,, 
which  has  physical  properties  essentially  its  own.  The  physical 
properties  of  homogeneous  mixed  crystals,  such  as  specific  gravity, 
refractory  index,  etc.,  are  continuous  functions  of  the  composition 
and  in  fact  such  crystals  behave  so  much  like  intimate  mechanical 
mixtures  or  mixed  liquids  that  they  are  frequently  spoken  of  as 
solid  solutions.  Such  mixtures,  as  a  whole,  cannot  appear  to  fol- 
low the  law  of  definite  proportions  but  on  careful  study  of  their 
constituents  they  can  all  be  resolved  into  groups  of  perfectly  definite 
composition. 

For  purposes  of  convenience  such  minerals  are  often  considered 
as  formed  by  the  replacement  of  one  element  or  radical  by  another 
isomorphous  with  it  rather  than  as  a  mixture  of  different  individual 
molecules.  Mutually  replaceable  isomorphous  elements  and  rad- 
icals occurring  in  minerals  as  given  by  Miers  *  are  as  follows  : 

H,  K,  Rb,  Cs,  Na,  Li,  NH4,  in  the  haloids,  nitrates,  phosphates 
and  silicates. 

F,  Cl,  Br,  I,  OH,  in  the    haloids,  phosphates  and  silicates. 

Au,  Ag,  Hg,  Cu',  Tl,  in  the  sulphides  and  sulpho-salts. 

Be,  Zn,  Mg,  Fe,  Mn,  Cu",  Ca,  in  the  phosphates  and  silicates. 

Mg,  Zn,  Fe,  Mn,  Ni,  Co,  in  the  sulphates. 

Ca,  Ba,  Sr,  Mg,  Pb,  Zn,  Fe,  Mn,  in  the  carbonates  and  sulphates. 

Fe,  Ni,  Co,  Mn,  Zn,  Cd,  in  the  sulphides  and  sulpho-salts. 

Al,  Fe'",  Cr,  Mn"',  in  the  oxides,  aluminates,  phosphates  and 
silicates. 

Si,  Ti,  Zr,  Sn,  Pb,  in  the  oxides  and  silicates. 

S,  Se,  Te,  in  the  sulphides  and  sulpho-salts. 

P,  V,  As,  in  the  phosphates,  etc. 

As,  Sb,  Bi,  in  the  oxides,  sulphides  and  sulpho-salts. 

Mo,  W,  in  the  oxides,  molybdates,  etc. 

Y,  Er,  Ce,  La,  Di,  in  the  haloids,  phosphates,  silicates,  etc. 

*  Miers,  Mineralogy,  p.  217. 


CHEMICAL    COMPOSITION  AND   REACTIONS.  183 

The  principle  of  isomorphic  replacement  is  well  illustrated  in  the 
garnets  which  have  the  class  formula 

R3"R2'"(Si04)3 

in  which  R"  stands  for  any  combination  of  the  isomorphous  divalent 
atoms   Ca,  Mg,  Fe",  Mn  taken  three  at  a  time  and  R'"  denotes 
any  combination  of  the  isomorphous  trivalent  atoms  Al,  Cr  or  Fe'". 
Therefore  while  the  typical  species 

Grossularite,  Ca3Al2(SiO4)3 

Pyrope,  Mg3Al2(SiO4)3 

Almandite,  Fe3Al2(SiO4)3 

Spessartite,  Mn3Al2(SiO4)3 

Andradite,  Ca3Fe2(SiO4)3 

Uvarovite,  Ca3Cr2(SiO4)3 

have  the  formulas  assigned  to  them  when  pure  they  are  in  fact 
seldom  found  on  analysis  to  more  than  approach  these  formulas 
since  their  divalent  element  may  be  replaced  by  any  one  of  the  iso- 
morphic group  Fe",  Mg,  Mn,  or  Ca  while  their  trivalent  element 
may  be  any  combination  of  Fe'",  Al  or  Cr.  Accordingly  garnets 
vary  through  all  combinations  of  color,  with  wide  divergence  of 
composition.  Still  their  crystalline  forms  are  identical  and  their 
composition  can  be  expressed  as  of  a  definite  type.  This  varia- 
bility of  composition  can  be  due  to  two  causes,  (i)  a  replacement 
of  elements  within  the  molecule  or  (2)  a  crystalline  mixture  of 
different  molecules  of  the  group  which  in  the  case  of  the  garnets 
is  generally  homogeneous. 

Homogeneity  is  not,  however,  an  essential  of  crystals  for  the 
center  of  a  crystal  may  vary  greatly  from  the  outer  surface  or  the 
two  ends  be  different  in  color,  as  is  so  frequently  seen  in  the  tour- 
malines, but  the  different  kinds  of  molecules  which  have  crystallized 
together  must  be  isomorphous. 

Most  minerals  are  isomorphic  mixtures.  They  have,  as  a  rule, 
been  formed  by  crystallization  either  from  solution,  from  fusion,  or 
more  rarely  by  the  condensation  of  sublimed  vapors.  Some,  as 
limonite,  have  been  formed  by  a  process  of  sedimentation  but  such 
are  uncrystallized,  and  are  generally  quite  impure.  Others  are  the 
results  of  alteration  from  atmospheric  agencies  and  frequently  con- 
tain in  the  same  specimen  the  original  mineral  and  its  alteration 
product. 


1 84  DESCRIPTIVE  MINERALOGY. 

Whenever  a  mineral  has  crystallized  from  solution  or  from  fu- 
sion it  is  always  more  or  less  modified  by  the  elements  which  may 
be  present  and  which  are  foreign  to  its  own  typical  structure. 
Three  cases  present  themselves  : 

r-  I.  If  the  liquid  contains  no  other  substance  than  the  compound 
of  which  the  mineral  is  made  then  it  crystallizes  out  in  a  state  of 
purity  and  is  as  definite  in  its  composition  as  any  compound  made 
in  the  laboratory. 

2.  If  the  liquid  contains  several  other  substances  but  none  which 
is  isomorphous  with  the  compound  of  which  the  mineral  is  made,  it 
may  crystallize  in  all  degrees  of  purity,  tending  always  to  form 
crystals  of  definite  composition  but  the  composition  of  the  mass 
varying  with  the  degree  with  which  the  liquid  is  saturated  with 
the  foreign  substances.     This  gives  rise  usually  to  a  series  of  frac- 
tional crystallizations  especially  apparent  in  beds  of  rock  salt  or  in 
mica  and  orthoclase  veins.     If  the  substances  are  in  solution  that 
one  is  first  deposited  whose  saturation  point  is  first  reached  by  any 
process  of  concentration,  the  others  following  in  their  respective 
order.     Where  the  case  is  one  of  fusion  those  substances  with  the 
highest  melting  points  will  tend  to  crystallize  out  first  and  in  a 
state  of  comparative  purity. 

3.  The  liquid  may  contain  two  or  more  isomorphic  compounds 
in  which  case  the  resulting  mineral  will  contain  each  of  these  sub- 
stances usually  in  about  the  relative  proportion  in  which  they  were 
present. 

Isomorphic  compounds  are  generally  salts  of  the  same  acids 
with  the  metallic  elements  different,  but  this  is  not  always  the  case, 
for  acid  radicals  may  also  replace  each  other. 

Composition  and  Formula. 

It  will  thus  be  seen  that  many  factors  besides  the  results  of  analy- 
sis must  be  taken  into  consideration  in  giving  a  formula  to  any 
mineral.  When,  however,  the  errors  of  calculation,  arising  from 
the  impurities  and  from  the  replacing  of  certain  elements  by  others 
of  different  atomic  weight  but  isomorphous  with  them,  are  elimi- 
nated, it  is  generally  possible  to  assign  a  typical  formula  to  the 
species.  The  difficulty  becomes  greater  when  the  polysilicates  and 
some  other  complicated  minerals  are  studied  and  in  no  case  must 
the  formula  for  the  species  be  considered  as  absolutely  invariable 
for  the  individual.  The  results  of  alteration  through  atmospheric 


CHEMICAL    COMPOSITION  AND   REACTIONS.  185 

agencies,  infiltration  of  water,  etc.,  tend  at  times  to  so  alter  the  in- 
dividual that  its  composition  varies  widely  from  the  type  while  at 
times  this  alteration  is  carried  on  so  regularly  and  so  far  that  new 
species  of  quite  definite  composition  are  formed.  In  expressing 
the  composition  by  formulas  the  ordinary  chemical  symbols  are 
used.  The  letter  R  is  used  to  represent  a  varying  group  of  iso- 
morphic  or  equivalent  elements,  and  it  may  have  the  valency  of 
these  elements  designated  by  dots  above  and  to  the  right  of  the 
letter.  When  two  elements  as  (Fe.Mg)  are  placed  in  parenthesis 
with  a  period  between  it,  indicates  that  the  two  replace  each  other 
in  all  proportions  in  the  different  individuals  of  the  species.  True 
molecular  formulas  can  not  be  given  to  minerals  for  they  are 
volatile  or  soluble  only  in  rare  instances.  The  symbols  therefore 
represent  little  more  than  the  relative  proportions  of  the  elements 
expressed  in  equivalents  of  their  atomic  weights,  i.  e.,  empirical 
formulas.  Most  minerals  can,  however,  be  considered  as  derived 
from  known  or  hypothetical  inorganic  acids,  and  in  many  instance* 
they  have  been  artificially  produced  in  the  laboratory  as  salts  of 
these  acids.  Thus  calcite,  CaCO3,  is  a  derivative  of  carbonic  acid, 
H2CO3 ;  fluorite,  CaF2,  of  hydrofluoric  acid,  HF ;  zircon,  ZrSiO4, 
of  orthosilicic  acid,  H4SiO4,  etc.  These  derivatives  may  be  nor- 
mal, acid,  or  basic  salts.  In  normal  salt  all  of  the  hydrogen  of  the 
acid  has  been  replaced  by  a  metallic  element  or  elements.  In  acid 
salts,  which  are  rare  except  perhaps  in  silicates,  only  part  of  the 
hydrogen  has  been  replaced.  In  basic  salts  more  metallic  atoms 
or  radicals  are  present  than  are  equivalent  to  the  hydrogen  of  the 
acid.  Minerals  may  therefore  be  classified  into  various  types 
according  to  their  derivation. 

Types. 

The  most  prominent  types  found  among  minerals  are  as  follows : 

1.  The  ELEMENTS,  as  Au,  Ag,  Cu,  Sb,  C,  S.     These  are  fre- 
quently alloyed  with  other  elements  as  copper  with  silver,  sulphur 
with  selenium,  etc. 

2.  The  OXIDES  and  HYDROXIDES  for  which  water,  H2O,  serves  as 
a  type,  as  cuprite,  Cu2O,  brucite,  Mg(OH)2.     It  is  not  necessary 
that  the  hydrogen  atom  or  atoms  be  replaced  by  a  single  element. 
This  replacement  may  be  by  a  group  of  elements  as  in  diaspore, 
AIO(OH)  or  on  the  other  hand  the  oxygen  may  be  partially  re- 
placed by  sulphur  as  in  kermesite,  Sb2S2O. 


1 86  DESCRIPTIVE  MINERALOGY, 

3.  The  SULPHIDES,  derivatives  of  H2S,  and  to  a  less  extent  their 
analogues  the  SELENIDES,  TELLURIDES,  ARSENIDES  and  ANTIMONIDES, 
as  galenite,  PbS,  clausthalite,  PbSe,  hessite,  Ag2Te,  niccolite,  NiAs. 
The  hydrogen  may  be  replaced  by  more  than  one  element  as  in 
chalcopyrite,  CuFeS2,  or  the  sulphur  may  be  partially  replaced  by 
arsenic  as  in  arsenopyrite,  FeAsS,  by  antimony  as  in  ullmannite, 
NiSbS,  and  also  by  selenium  and  by  tellurium,  but  to  a  less  extent 
and  with  smaller  tendency  to  form  distinct  species. 

4.  The  CHLORIDES,  derivatives  of  HC1,  and  to  a  less  extent  their 
analogues  the  FLUORIDES,  BROMIDES,  and  IODIDES  as  halite,  NaCl, 
fluorite,  CaF2,  bromyrite,  AgBr,  iodyrite,  Agl. 

More  than  one  metal  may  replace  the  hydrogen  as  in  the  double 
fluoride  cryolite,  Na3AlF6,  and  chlorides,  bromides,  iodides  or 
fluorides  may  crystallize  together  as  in  embolite,  Ag(Cl.Br). 

5.  NITRATES,  derivatives  of  HNO3,  as  nitre,  KNO3;  soda  nitre, 
NaNO3;  isomorphic  or  basic  modifications  are  rare. 

6.  CARBONATES,  derivatives  of  H2CO3,  as  calcite,  CaCO3 ;  sider- 
te,  FeCO3,  etc.      Isomorphic   combinations  are  common.      The 
carbonates  of  Zn,  Fe,  Mn,  Ca  and  Mg  are  isomorphous,  and  also 
the  carbonates  of  Ca,  Ba,  Sr  and  Pb.     Consequently,  minerals  con- 
taining various  combinations  of  these  carbonates  are  found.     Many 
basic  salts  of  carbonic  acid  also  occur,  as  malachite,  Cu2(OH)2CO3 ; 
azurite,   Cu2(OH)2(CO3)2.      Carbonates  are  also  frequently  found 
containing  water  of  crystallization  as  natron,  Na2CO3  +  ioH2O. 
In  a  few  instances  a  carbonate  and  a  halogen  salt  crystallize  to- 
gether as  in  phosgenite,  Pb2Cl2CO3. 

7.  SULPHATES,  derivatives  of  H2SO4,  as  anhydrite,  CaSO4 ;  barite, 
BaSO4,  etc.     Isomorphic  combinations   are   more   common  than 
simple  sulphates.     Among  double  salts  may  be  noted  sulphates 
containing  two  or  more  metals,  as  glauberite,  Na2SO4.CaSO4;  those 
containing  a  sulphate  and  chloride,  as  kainite,  MgSO4.KCl  -f  3H2O. 
Basic  sulphates  are  also  numerous,  as  brochantite,  Cu2(OH)2SO4.- 
2Cu(OH)2,  and  some  individuals  of  any  of  the  previous  types  crys- 
tallize with  water  of  crystallization,  as  copiapite,  Fe2(FeOH)2(SO4)5 
-f  i8H2O. 

8.  CHROMATES,  derivatives  of  H2CrO4,  as  crocoite,  PbCrO4,  and 
derivatives  of  HCrO2,  as  chromite,  FeCr2O4.     These  are  the  two 
important  mineral  chromates.     Two  or  three  rare  basic  compounds 
are  also  known. 


CHEMICAL    COMPOSITION  AND   REACTIONS.  1 87 

9.  MOLYBDATES,  derivatives  of  H2MoO4,  as  Wulfenite,  PbMoO0 
which  is  the  only  important  natural  molybdate. 

10.  TUNGSTATES,  derivatives  of  H2WO4,  as  scheelite,  CaWO4. 
Tungstates  also  are  rare.     One  or  two  isomorphic  combinations 
are  known,  as  in  wolframite,  (Fe.Mn)WO4,  powellite,  Ca(Mo,  W)O4« 

11.  BORATES,  derivatives  of  HBO2,  H3BO3   or  of  H2B4O7,  as 
sassolite,    H3BO3;    borax,    Na2B4O7  +  ioH2O.      Metaborates   are 
rare.     Ulexite,  CaNaB5O9  -(-  6H2O,  may  be  considered  as  a  mo- 
lecular combination  of  CaB4O7  +  NaBO2,  while  colemanite,  Ca2B6- 
Ou  +  5H2O,  would  consist  of  CaB4O7  +  Ca(BO2)2.     Most  natural 
borates  contain  water  of  crystallization,  and  a  few  basic  combina- 
tions are  found. 

1 2.  ALUMINATES,  derivatives  of  H A1O2,  as  spinel,  Mg(AlO2)2 ; 
chrysoberyl,  Be(AlO2)2.     The  aluminates  are  isomorphous  with  the 
ferrates  and  metachromates,  consequently  the  Al  may  be  partially 
replaced  by  Fe  or  Cr,  while,  on  the  other  hand,  the  common  alu- 
minates are  themselves  isomorphous,  and  the  Mg,  Fe,  Zn  and  Mn 
salts  replace  each  other  in  their  characteristic  spinels  to  a  limited 
extent. 

13.  PHOSPHATES,  derivatives  of  H3PO4,  as  vivianite,  Fe3(PO4)2  -f- 
8H2O.     By  far  the  majority  of  mineral  species  of  phosphates  are 
either  isomorphic    modifications   or   basic   salts,  both  with   and 
without  water  of  crystallization.     Simple  phosphates  may  crystal- 
lize together,  as  in  triphylite,  Li(Fe.Mn)PO4.     Phosphates  may 
crystallize  with  chlorides  and  fluorides,  as  in  apatite,  Ca5(Cl.F)(PO4)3. 
Basic  salts  may  be  simple,  as  in  turquois,  A12(OH)3PO4  +  H2O,  or 
may  contain  several  metals,  as  in  lazulite,  (Mg.Fe.Ca)Al2(OH)2- 
(P04)2. 

14.  ARSENATES,  derivatives  of  HsAsO4,  form  compounds  very 
similar  to  the  phosphates  in  molecular  structure,  as   scorodite, 
FeAsO4  +  2H2O,  a  hydrous  ferric  arsenate;  mimetite,  3Pb3(AsO4)2 
+  PbCl2,  a  combination  of  the  isomorphic  arsenate  and  chloride ; 
olivenite,  Cu2(OH)AsO4,  a  basic  copper  arsenate.     Also  a  few  rare 
antimonates. 

15.  SULPHARSENITES,  derivatives  of  H3AsS.}  and  their  analogues 
the  SULPHANTIMONIDES,  are  frequently  classed  with  the  sulphides 
but  are  more  properly  derived  from  hypothetical  acids  similar  to 
H.;AsO3,  etc.,  in  which    the  oxygen  is  replaced   by  sulphur,  as 
proustite,  Ag3AsS3 ;  pyrargyrite,  Ag3SbS3. 


1 88  DESCRIPTIVE  MINERALOGY. 

1 6.  VANADIXATES,  COLUMBATES  and  TAXTALATES,  derivatives  of 
H3VO4,  HCbO3  and  HTaO3.  The  chief  vanadinates  are  vanadinite, 
3Pb3(VO4)2  +  PbCl2,  a  molecular  combination  of  lead  vanadinate 
and  chloride,  and  descloizite  (Pb.Zn)  (Pb.OH)VO4,  a  basic  lead 
vanadinate  containing  zinc.  The  most  important  natural  columbate 
is  the  mineral  columbite,  Fe(CbO3)2.  The  most  prominent  tantalate 
is  tantalite,  Fe(TaO3)2. 

1 6.  SILICATES.  —  By  far  the  largest  number  of  minerals  known 
fall  under  this  subdivision.  They  may  generally  be  considered  as 
derived  from  orthosilicic  acid,  H4SiO4,  metasilicic  acid,  H2SiO3,  or 
some  one  of  the  hypothetical  polysilicic  acids,  H2Si2O5,  H4Si3O8, 
H8Si3O10  or  H6Si2O7.  These  polysilicic  acids  may  be  considered  as 
derived  from  one  or  more  molecules  of  orthosilicic  or  metasilicic 
acid  by  the  elimination  of  water.  Isomorphic  combinations  are  the 
rule,  and  these  combinations  are  at  times  so  complicated  that  it  is 
almost  impossible  to  give  even  a  typical  formula  to  the  species. 
Basic  and  acidic  salts  are  common,  but  the  silicates  do  not  show 
as  great  tendency  to  crystallize  with  water  of  crystallization  as  is 
possessed  by  some  of  the  other  classes  of  compounds.  Those 
which  do  contain  water  of  crystallization  are  commonly  considered 
in  a  class  by  themselves,  on  account  of  their  many  resemblances. 
The  basic  elements  most  commonly  replacing  each  other  are 
Ca,  Mg,  Fe,  Zn  and  Mn;  Na,  Li  and  K,  and  Al,  B,  Cr  and  Fe. 
The  silicon  is  itself  sometimes  partially  replaced  by  Al,  as  in 
anorthite,  or  by  Ti,  as  in  titanite. 

Calculation  of  Formulas. 

In  expressing  the  composition  of  a  mineral  by  a  formula  we 
have  only  the  atomic  weights  of  its  component  elements  and 
the  results  of  analysis  from  which  to  calculate.  Hence  the 
formulas  given  do  not  of  necessity  express  the  structure  of  the 
molecule,  but  only  the  composition  ratio.  In  fact,  the  symbols 
adopted  are  always  the  simplest  which  can  express  the  propor- 
tions shown  by  analysis  to  exist  between  the  atoms  and  which 
satisfy  their  valences.  The  true  molecular  formulas  are  proba- 
bly always  some  unknown  multiple  of  these  symbols.  For  the 
purposes  of  mineralogy,  however,  the  composition  formulas  are 
sufficient. 

An  example  may  make  this  point  clearer.  A  very  pure  speci- 
men of  beryl  gave  the  following  results  on  analysis : 


CHEMICAL    COMPOSITION  AND   REACTIONS.  189 

Per  cent. 

BeO, 14.01 

AI2O3. 19.26 

SiO2 66.37 

The  sum  of  the  atomic  weights  for  each  group  is : 

BeO  =  25. 
A12O3=  102. 
SiO2  =  60. 

The  results  of  analysis  represent  the  proportion  in  which  the 
groups  are  present  in  the  molecule.  Consequently,  the  relation 
between  the  number  of  groups  must  be  : 

Percentage  Atomic  Proportionate 

Composition.  Weights.  Number  of  Groups. 

14.01  -f  25  .56 

19.26  102  =  .189 

66.37         -f         60         =  1.106 

Now,  as  fractional  atoms  cannot  exist,  our  problem  is  simply  to 
find  the  smallest  number  of  whole  groups  which  stand  to  each 
other  in  this  relation,  and,  as  .56  :  .189  :  1.106  =  3  :  i  :  6,  very 
nearly,  therefore,  the  composition  is  represented  by  3  BeO  +  A12O3 
-f  6SiO2,  which  may  be  better  written  Be.HAl2Si6O18,  or,  as  it  at  once 
becomes  evident  that  the  proportion  between  silicon  and  oxygen 
is  that  of  a  metasilicate,  Be3Al2(SiO3)6. 

It  will  now  be  found,  on  calculating  the  theoretical  percentage 
composition  of  Be3Al2(SiO3)6,  that  it  agrees  within  the  limits  of 
error  with  that  found  by  analysis,  and  as  the  twelve  affinities  of 
the  six  SiO3  radicals  are  satisfied  by  those  of  Be  and  Al  atoms,  the 
formula  probably  represents  the  composition  of  the  compound. 
The  true  molecular  formula  is,  however,  ;/Be3Al2(SiO3)6  wherein  n 
represents  some  whole  number. 

The  calculation  is  not  generally  as  simple  as  the  above  example 
might  indicate.  Usually,  minerals  contain  elements  which  seem 
foreign  to  their  true  composition,  and  which  are  present  either  as 
impurities  or  which  replace  analogous  elements  of  the  true  mole- 
cule. In  fact,  many  beryls  contain  Cs,  H2,  Na2,  Ca,  or  Mg 
replacing  Be  ;  and  Fe  or  Cr  replacing  Al.  Such  replacing  ele- 
ments, if  present  only  in  small  quantities,  must  be  converted  into 


190  DESCRIPTIVE  MINERALOGY. 

their  equivalents  of  Be  or  Al  before  the  calculation  for  formula  is 
made. 

In  perhaps  the  majority  of  cases  the  calculation  of  formula  is  an 
extremely  complicated  matter.  The  silicates  especially  are  subject 
to  great  variation  in  composition  and  in  some  cases  it  is  only  after 
examining  and  carefully  comparing  many  analyses,  eliminating  iso- 
morphous  elements  and  their  acid  equivalents  from  the  whole,  com- 
paring the  results  with  calculations  on  hypothetical  compounds, 
etc.,  that  even  an  approximate  formula  can  be  given.  Much  insight 
is  also  obtained  at  times  from  artificial  reproductions  in  the  lab- 
oratory. Again  when  minerals  are  known  to  be  closely  related 
their  analyses  are  carefully  studied  with  special  reference  to  see 
whether  by  the  elimination  of  certain  groups,  which  may  be  iso- 
morphic,  their  chemical  relation  may  not  become  apparent  and  their 
analogy  shown  by  formula. 

No  representative  formula  can  ever  be  assigned  from  an  analy- 
sis of  impure  material  unless  the  nature  and  extent  of  the  impuri- 
ties are  known. 

Clues  are  often  obtained  as  to  the  constitution  of  the  molecule 
which  are  entirely  foreign  to  the  percentage  composition,  but  which 
materially  assist  in  the  construction  of  the  formula.  Thus  H2O, 
present  as  water  of  crystallization,  is  driven  off  at  comparatively 
low  temperatures,  while  the  hydrogen  of  hydroxides  or  of  acid  or 
basic  salts  is  usually  expelled  as  water  only  under  a  temperature 
approaching  that  of  ignition.  Orthosilicates  are  known  to  be  much 
less  stable  than  metasilicates,  and  frequently  are  found  altered  to 
metasilicates.  This  fact  sometimes  aids  in  determining  the  for- 
mula of  a  compound  which  otherwise  might  be  referred  to  either 
class.  For  instance,  analytical  results  have  been  obtained  for  both 
andalusite  and  cyanite,  which  are  satisfied  by  the  formula  Al2SiO5. 
This  represents  more  oxygen  than  is  present  in  any  of  the  silicic 
acids,  and  part  of  the  oxygen  is  therefore  undoubtedly  in  com- 
bination with  the  aluminium.  Two  rational  formulas  now  become 
possible,  one  an  orthosilicate  Al(AlO)SiO4,  the  other  a  metasilicate 
(AlO)2SiO3.  Andalusite  is  much  more  easily  decomposable  than 
cyanite,  which  is  not  so  easily  altered.  The  first  symbol  is  there- 
fore assigned  to  andalusite  and  the  second  to  cyanite. 


CHAPTER  XX. 
THE   OCCURRENCE   AND  ORIGIN   OF  MINERALS. 

OVER  ninety-nine  per  cent,  of  that  portion  of  the  earth's  crust 
which  has  been  examined  is  estimated  *  to  consist  of  nine  elements 
in  the  following  proportions : 

O,      49.98  Fe,      5.08  Na,     2.28 

Si,      25.30  Ca,      3.51  K,       2.23 

Al,       7.26  Mg,     2.50  H,      0.94 

Practically  none  of  these  exists  in  the  free  state,  but  combined 
principally  as  silicates  and  oxides  and,  with  rarer  elements,  as  car- 
bonates, haloids  and  sulphates.  The  unoxidized  products,  such 
as  sulphides,  are  comparatively  rare  and  usually  restricted  to 
special  localities. 

In  considering  the  origin  of  a  species,  it  must  not  be  forgotten 
that  it  may  originate  in  several  genetically  distinct  ways.  Tscher- 
mak  instances  hematite,  Fe2O3,  in  six  genetic  varieties  : 

(a)  Rhombohedral  crystals  on  druses  with  quartz  and  adular  apparently  directly 
from  solution. 

(  b  )   Distorted  plates  in  lava  from  volcanic  emanations. 

(  c  )   Fibrous  red  hematite  formed  by  loss  of  water  from  limonite. 

(</)   Dense  red  hematite  in  pyrite  forms,  evidently  from  pyrites. 

(  e  )   Dense  red  hematite  in  siderite  forms,  evidently  from  siderite. 

(/)  Dense  red  hematite  pseudomorphic  after  calcite  shells,  evidently  a  precipitate 
by  CaCOs. 

IMPORTANT   SOURCES   OF   INFORMATION   AS    TO   ORIGIN. 

1.  Paragenesis  or  The  Story  of  Associates. 

2.  Alteration  and  Pseudomorphs. 

3.  Physical  and  Chemical  Characters. 

4.  Synthetic  Production. 
Paragenesis. 

The  term  paragenesis  is  used  to  express  the  relations  between 
associated  minerals.  This  association  may  be  accidental,  as  in  a 
conglomerate,  but  the  association  in  the  rock  in  which  they  were 
formed  may  reveal: 


*  F.  W.  Clarke,  U.  S.  Geol.  Survey,  Bull.  78. 


192  DESCRIPTIVE  MINERALOGY. 

(a]  Simultaneous  origin  in  that  sometimes  one  is  upon  or  enclosed 
in  the  other  and  sometimes  this  is  reversed. 

(b]  Epigencsis  in  that  one  species  is  derived  from  the  other  as  in 
pseudomorphs  and  other  alterations. 

(c]  Succession  or  order  of  deposition  by  relative  position,  as  in 
many  ore  veins  the  sides  are  older  than  the  centers,  or  in  granite 
the  quartz  kernels  took  shape  only  after  the  mica  and  feldspar ;  or 
in  porphyry  where  the  larger  enclosed  crystals  of  quartz  or  ortho- 
clase  are  older  than  the  little  ones  which  make  the  mass. 

(d}  Repetition.  The  same  species  may  be  repeated ;  for  instance, 
the  first  generation  in  dull  simple  crystals,  the  second  in  bright 
highly  modified  forms,  or  there  may  be  a  secondary  enlargement 
as  of  the  quartz  grains  in  a  sandstone. 

(e)  Related  Chemical  Composition.  Some  element  or  group  of 
elements  may  be  common  to  all  the  associates  ;  for  instance,  fluorine 
in  the  associates  of  cassiterite  and  sodium  in  the  minerals  of 
phonolite. 

Alteration  and  Pseudomorphs. 

Minerals  are  constantly  undergoing  alteration  and  each  altera- 
tion tends  to  result  in  new  species,  because  the  solutions  of  minerals 
in  one  rock  are  frequently  carried  into  contact  with  species  and 
solutions  from  other  sources  and  new  less  soluble  compounds  result. 

Two  general  classes  of  alteration  may  be  recognized :  ( i ) 
Changes  which  are  essentially  structural,  involving  a  molecular 
rebuilding  but  without  change  of  material.  (2)  Changes  which 
are  essentially  chemical  involving  the  taking  away  or  adding  of 
certain  elements  or  even  the  entire  removal  of  one  substance  and 
its  replacement  by  another. 

The  change  may  be  merely  superficial  or  may  affect  whole 
mountain  masses  ;  it  may  affect  all  minerals  of  a  rock  or  only 
one. 

The  most  frequently  observed  alterations  are  anhydrous  silicates 
to  hydrous  silicates  or  sulphides  to  hydrous  sulphates  and  hydrates, 
but  changes  from  one  anhydrous  mineral  to  another  also  take 
place,  as  leucite  to  orthoclase,  pyroxene  to  amphibole,  calcite  to 
aragonite. 

The  causes  of  alteration  are  principally  the  natural  watery  solu- 
tions, which  will  be  discussed  later,  and  the  mountain  pressures 
which  open  capillary  fissures  in  the  minerals  and  force  the  ground 


OCCURRENCE  AND    ORIGIN  OF  MINERALS.  193 

waters  into  these.  Other  alterations  are  by  action  of  gases  and 
vapors  at  high  temperatures. 

Frequently  minerals  are  found  as  "  pseudomorphs,"  that  is,  in 
crystalloids,  the  shapes  of  which  belong  to  some  other  mineral. 
In  many  instances  these  are  merely  casts  or  incrustations  which 
prove  little  as  to  the  process,  but  in  other  instances  they  are  evi- 
dently the  result  of  the  gradual  and  often  incomplete  alteration  of 
the  original  mineral  and  give  important  clues  to  the  process  of 
alteration  and  add  weight  to  synthetic  experiments  by  showing 
that  in  nature  similar  changes  actually  occur. 

Petrifactions  differ  from  pseudomorphs  principally  in  that  they 
are  alterations  or  replacement  of  organic  remains  by  mineral  sub- 
stances. 

Physical  and  Chemical  Characters. 

Any  conclusion  as  to  the  origin  or  mode  of  formation  of  a  min- 
eral must  be  in  conformity  with  its  observed  physical  and  chemical 
characters.  For  instance,  the  solubility  is  a  most  important  factor 
in  determining  the  order  of  separation  whether  from  aqueous  or 
fusion  solutions.  Leucite  crystals  are  isometric  in  shape,  but  their 
optical  characters  indicate  a  system  of  lower  symmetry  unless  the 
material  is  heated  to  433°  C.,  the  conclusion  is  that  these  isometric 
crystals  formed  above  433°.  Cyanite  at  about  the  melting  point 
of  copper  assumes  the  characters  of  sillimanite,  hence,  ignoring 
the  effect  of  pressure,  it  formed  below  that  temperature. 

Synthetic  Production  of  Species  and  of  Alterations. 

The  successful  reproduction  of  a  mineral  by  a  method  which 
does  not  conflict  with  the  known  natural  conditions  is  an  important 
clue  as  to  its  probable  origin,*  but  is  not  conclusive,  for  the  same 
species  is  often  made  in  several  ways.  For  instance :  ortho- 
clase  has  been  formed  from  fused  magma,  from  sublimation  and  in 
the  wet  way  and  by  action  of  solutions  on  leucite,  and  galenite  has 

*  The  production  of  species  synthetically  has  several  other  purposes,  such  as  settling 
the  composition  : 

(a)  By  producing  crystals  identical  in  characters  with  those  of  some  natural  sub- 
stance but  avoiding  the  frequent  natural  inclusions,  weathering,  etc.,  which  lead  to 
varying  analyses. 

(/;)   Obtaining  crystals  of  massive  or  poorly  crystallized  minerals. 

(c)  Obtaining  simple  types  which  are  rare  in  nature  and  finding  new  members  of 
series. 


194  DESCRIPTIVE  MINERALOGY. 

been  formed  by  sublimation,  by  electrochemical  reactions  and  by 
superheated  water  in  a  sealed  tube. 

On  the  other  hand,  probable  theories  which  have  not  been  synthe- 
tically checked  are  not  necessarily  wrong.  The  processes  of  nature 
are  not  all  to  be  reproduced,  especially  the  geologic  periods  of  time. 

So  also  the  alteration  of  a  mineral  in  the  laboratory  or  even  the 
production  of  pseudomorphs  by  possible  natural  methods  may 
be  of  value  as  indicating  what  would  happen  under  similar  condi- 
tions maintained  longer  periods. 

The  method  of  synthesis  chosen  must  conform  as  far  as  possible 
with  the  observed  conditions,  must  employ  reagents  that  occur  in 
nature  and  are  thought  to  have  taken  part  in  the  making.  Geo- 
logic time  may  be  in  part  compensated  for  by  increased  pressure 
and  a  temperature  of  100°  to  300°;  microscopic  crystalline  crusts 
must  often  be  accepted  as  the  equivalent  of  larger  natural  crystals. 

i.  THE  PRIMARY  MINERALS  FORMED  BY  SEPARATION 
FROM  FUSION  SOLUTIONS. 

If  the  earth  solidified  by  the  cooling  of  a  mass  of  incandescent 
vapors  the  first  crust  must  have  floated  on  a  hot  pasty  mass  and 
must  have  cooled  very  slowly,  forming  crystalline  rock.  Whether 
any  of  this  original  crust  still  exists  or  not  the  conditions  and  re- 
sults must  have  been  very  similar  to  those  at  the  formation  of  the 
existing  igneous  rocks. 

Below  the  present  crust  *  of  the  earth  the  regularly  increasing 
temperature  and  pressure  indicate  that  at  some  depth  everything 
must  be  fluid  f  and  homogeneous.  This  fluid  mass  or  magma 
under  the  enormous  pressure  due  to  its  depth  is  forced  up  into  any 
crack  or  crevice  in  the  crust  above,  sometimes  reaching  and  over- 
flowing at  the  surface  (volcanic  rocks),  at  other  times  being  forced 
between  strata  far  below  the  surface  (plutonic  rocks). 

In  either  case  there  is  a  diminished  pressure  and  temperature, 
more  rapid  in  the  case  of  the  volcanic  rocks,  and  the  composition 
often  changes  by  exhalation  of  volatile  constituents  and  the  solidifi- 
cation commences. 

*The  very  widely  distributed  foliated  rocks  known  as  gneiss  and  crystalline  schist 
are  often  regarded  as  the  original  rocks,  owing  their  foliated  structure  to  dynamic 
changes,  slipping,  faulting,  etc.  Their  minerals  include  the  constituents  of  granite  and 
other  minerals  which  are  the  results  of  change. 

f  And  deeper  still  again  solid. 


OCCURRENCE  AND    ORIGIN  OF  MINERALS.  195 

The  Nature  of  a  Magma. 

This  fluid  magma  is  a  fusion  solution  of  silicates  strictly  analo- 
gous to  an  aqueous  solution  of  several  salts  and  the  order  of  sepa- 
ration rests  not  upon  fusibility  but  upon  solubility.  The  nearly 
infusible  leucite,  for  instance,  in  a  leucite-tephrite  magma  goes  into 
a  solution  at  a  little  above  red  heat  and  separates  at  a  red  heat. 

The  Minerals  which  Form  a  Silicate  Magma. 

Two  principles,  the  second  a  corollary  of  the  first,  seem  to  govern 
the  order  of  separation. 

1.  The  least  soluble  mineral  separates  first  and  separates  only 
when  for  the  existing  pressure  and  temperature  the  magma  is  super- 
saturated with  the  substance. 

2.  Substances  present  in  least  amount  separate  first,  that  is,  the 
less  needed  to  saturate  the  earlier  the  separation.     According  to 
Lagorio  the  order  of  formation  will  be  : 

1.  Accessory  minerals.      Principally  zircon,  titanite,  magnetite, 
chromite,  ilmenite,  hematite,  rutile,  apatite,  pyrite,  pyrrhotite. 

2.  Silicates  of  Fe,  Mg.     Hypersthene,  enstatite,  chrysolite. 

3.  Silicates  of  (Mg,  Ca).     Pyroxene,  amphibole. 

4.  Silicates  of  (K,  Mg,  Fe,  Al).     Biotite. 

5.  Silicates  of  (Ca,  Al)  or  (Ca,  Na,  Al).     Plagioclase. 

6.  Silicates  of  (Na,  Al).     Albite,  nephelite,  sodalite. 

7.  Silicates  of  (K,  Al).     Orthoclase,  microcline,  leucite. 

8.  Free  silica.     Quartz. 

Essentially  the  same  mineral  species  are  found  in  the  volcanic 
rocks  and  in  the  deep-seated  or  plutonic  rocks,  but  certain  facts 
as  to  genesis  may  be  noted  in  each. 

In  the  Volcanic  Rocks. 

The  minerals  were  some  of  them  formed  at  the  release  of 
pressure,  as  is  indicated  by  the  innumerable  leucite  crystals  in  the 
volcanic  dust  and  swimming  in  the  molten  lava  of  Vesuvius  and  by 
the  augite,  chrysolite  and  labradorite  in  the  ash  of  y£tna,  and 
anorthite  in  the  lavas  of  Miyake,  Japan. 

The  formation  continues  after  eruption,  as  is  indicated  by  the 
fact  that  near  the  surface  of  a  lava  stream  where  the  cooling  is 
relatively  rapid  there  will  be  much  glass  and  minute  crystals,  but 
deeper,  less  glass  and  more  and  larger  crystals.  The  larger  crystals 
often  show  glassy  inclusions. 


196  DESCRIPTIVE  MINERALOGY. 

In  the  Plutonic  Rocks. 

The  minerals  of  the  granites,  syenites,  etc.,  though  essentially 
the  same  species  as  those  formed  in  volcanic  rocks,  and  though 
formed  undoubtedly  from  similar  magma,  show  certain  differences. 

They  are  not  connected  with  slaggy,  glassy  or  frothy  structures, 
do  not  often  contain  both  the  earlier  formed  large  and  the  later 
minute  crystals.  Glassy  inclusions  are  rare,  liquid  inclusions  are 
frequent.  All  these  point  to  a  slow  formation  under  pressure  and 
to  the  active  participation  of  water  in  their  formation. 

2.     CONTACT    MINERALS    AND    MINERALS    DUE    TO 
EXHALATIONS. 

Before  considering  the  great  group  of  minerals  formed  by  the 
aid  of  watery  solutions  two  minor  groups  may  be  mentioned,  which 
are  more  the  result  of  the  action  of  the  vapors  which  escape  from 
the  igneous  rocks  than  of  direct  separation  from  a  fused  magma. 

CONTACT  MINERALS. 

The  more  important  group  includes  the  minerals  commonly 
called  contact  minerals,  which  are  produced  when  an  igneous  rock 
penetrates  another  rock.  The  textures  of  both  rocks  change  and 
new  minerals  form,  at  the  contact  and  for  some  distance  from  it, 
which  are  undoubtedly  produced  by  the  simultaneous  action  of 
water,  high  temperature  and  pressure,  very  much  as  crystals  are  in 
the  Senarmont  sealed  tubes.  The  action  is  essentially  the  forma- 
tion of  new  compounds  from  the  constituents  of  the  rock  which  has 
been  penetrated  and  to  a  much  less  extent  from  those  of  the  in- 
truding rock  or  of  the  two  rocks  combined.  The  penetration  of 
the  superheated  water  is  perhaps  the  principal  agent,  acting  both 
to  recrystallize  and  as  a  chemical  agent,  and  hydrofluoric  and  boric 
acid  act  as  still  more  powerful  agents  though  less  in  amount.  The 
solution  of  fragments  in  the  magma,  changes  the  composition  and 
solvent  power  and  produces  different  minerals. 

The  contact  minerals  are  very  numerous,  the  principal  ones  being : 

Meta- Silicates.  —  Pyroxene,  wollastonite,  amphibole. 

Ortho-Silicates.  —  Garnet,  vesuvianite,  wernerite,  chiastolite,  epi- 
dote,  biotite,  phlogopite. 

Fluo-  or  Boro-Silicates.  —  Tourmaline,  topaz. 

Non-Silicates.  —  Magnetite,  pyrrhotite,  rutile,  graphite,  fluorite. 

For  instance,  an  impure  siliceous  limestone  in  contact  with  an 


OCCURRENCE  AND    ORIGIN  OF  MINERALS.  197 

eruptive  granite  would  probably  be  converted  into  a  granular  mar- 
ble containing  crystals  of  such  silicates  as  garnet,  wollastonite, 
vesuvianite,  wernerite,  pyroxene  and  amphibole.  If  boric  acid  and 
hydrofluoric  acid  were  given  off  tourmaline  and  topaz  might  form, 
and  so  on. 

MINERALS    DUE   TO   NATURAL   EXHALATIONS. 

Volcanoes  emit  steam  and  other  vapors,  often  at  first  O  and  N, 
mixed  about  as  in  air,  and  a  little  H,  and  later,  probably  by  the 
action  of  the  steam  and  the  high  temperature  in  decomposing  exist- 
ing compounds,  there  arise  vapors  of  HC1,  SO3,  SO2,  H2S  and  CO2. 

These  rising  vapors  act  on  the  sides  of  the  crevices  and  react 
upon  each  other,  producing  many  minerals  in  small  amounts,  the 
principal  groups  being  : 

Sulphur  by  the  reaction  SO2  +  2H2S  =  38  +  2H2O. 

Chlorides  by  the  action  of  HC1  on  the  adjacent  rocks. 

Sulphates  by  the  action  of  SO2  and  O  on  the  adjacent  rocks. 

Oxides  by  the  decomposition  of  chlorides  at  high  temperature. 

Carbonates  by  the  action  of  CO.,  on  the  oxides. 

If  the  flowing  lava  passes  over  vegetable  matter  sal-ammoniac 
(NH4C1)  is  formed. 

The  existence  of  exhalations  of  steam,  fluorine,  boric  acid  and 
chlorine  from  the  plutonic  rocks  appears  to  be  proved  by  the  alter- 
ations in  these  rocks. 

Sulphur  Deposits. 

The  massive  deposits  of  sulphur  and  of  the  sulphides  so  impor- 
tant as  ores  are  apparently  chiefly  due  to  H2S,  itself  of  volcanic 
origin.  Spezia  claims  that  even  the  Sicilian  sulphur  deposit,  so 
often  regarded  as  a  reduction  product  of  gypsum  (CaSO4  -f  2H2O), 
is  a  decomposition  of  H2S  and  that  the  gypsum  itself  is  due  to  the 
action  of  an  H2S  solution  on  limestone. 

3.  MINERALS  PRODUCED  BY  WATERY  SOLUTIONS. 

The  minerals  thus  far  described  are,  wherever  they  occur,  sub- 
ject to  perpetual  alteration  by  water  and  watery  solutions.  In 
addition  to  the  rain  water,  the  rivers,  lakes  and  seas,  the  water  in 
clefts  and  hollows  and  the  comparatively  freely  moving  waters  near 
the  surface  ;  a  so-called  "  ground  water,"  is  found  penetrating  the 
apparently  solid  rocks  at  great  depths,  filling  microscopic  clefts, 


198  DESCRIPTIVE  MINERALOGY. 

into  which  it  is  drawn  by  capillary  attraction  and  forced  by  the 
pressure  of  the  water  column  above.  So  general  is  it  that  almost 
any  fragment  of  rock  removed  to  a  dry  place  exudes  moisture  and 
loses  weight,  and  the  mountain  pressures  by  their  crushing  weight 
continually  produce  new  capillary  clefts  and  open  new  roads  for 
the  water. 

The  Solvent  Power  of  Pure  Water. 

Distilled  water  at  ordinary  temperatures  and  pressures  will  not 
only  dissolve  large  amounts  of  the  so-called  soluble  salts  but  small 
amounts  of  almost  all  other  substances,  for  instance,  in  per  cents, 
gypsum  0.25,  calcite  0.0025,  barite  0.0002  ;  anhydrous  silicates 
very  slightly  and  quartz  so  slightly  that  no  numbers  have  yet  been 
found  to  express  it.  Increased  temperature  and  pressure  in  gen- 
eral increase  solubility.  Wohler  dissolved  apophyllite  crystals  at 
1 80°  to  190°  and  10  to  12  atmospheres  pressure  and  by  cooling 
they  were  again  deposited. 

The  Solvent  and  Decomposing  Effect  of  Carbonated  Water. 

The  solvent  power  of  water  is  greatly  increased  by  the  presence  * 
of  CO2,  pressure  in  this  case  increasing  the  solvent  power,  but  in- 
creased temperature  diminishing  it. 

For  instance,  water  saturated  with  CO2  dissolved  o.  10  to  0.12 
per  cent,  of  calcite  or  forty  times  as  much  as  pure  water. 

More  important,  however,  as  bearing  upon  the  alteration  of  sili- 
cates, is  that  water  containing  carbonic  acid  or  alkaline  carbonates 
in  solution  will  decompose  many  silicates  f  forming  carbonates  with 
some  of  their  bases  and  either  free  silica  or  a  soluble  alkaline 
silicate  and  often  leaving  behind  silicates  of  aluminium,  iron  or 
magnesium. 

The  Effect  of  Other  Substances  in  Water. 

Free  oxygen  may  oxidize  sulphides  and  arsenides  and  further 
oxidize  oxides  or  even  drive  out  CO2,  for  instance  forming  hematite 
from  siderite,  4FeCO3  +  2O  +  3H2O  =  2Fe2O3  +  3H2O  -f  4CO2. 

Organic  materials  in  water  may  cause  reduction  to  lower  oxides 
or  native  metals,  and  of  alkaline  sulphates  to  sulphides,  which  then 

*  The  rain  passing  through  the  atmosphere  absorbs  about  1.25  per  cent,  nitrogen, 
.65  per  cent,  oxygen  and  .03  per  cent,  of  carbon  dioxide. 

f  For  example,  tremolite  may  be  converted  into  talc  and  calcite,  CaMgsSi4O12  +  CO2 


OCCURRENCE  AND    ORIGIN  OF  MINERALS.  199 

are  able  to  precipitate  sulphides  from  silicates,  carbonates  and  sul- 
phates of  the  metals.      Many  other  reactions  are  possible. 

THE  SEPARATION  OF  SOLID  COMPOUNDS  FROM  WATERY  SOLUTIONS. 
The  principal  methods  by  which  the  constituents  of  a  watery 
solution  are  separated  from  the  solution  as  solids  are : 

I.  Decreased  Solvent  Power  by  : 

.(a)  Decreased  pressure  or  temperature,  as  in  the  case  of  solutions 
rising  from  below. 

(fr)  Evaporation.  —  This  is  practically  restricted  to  the  seas  and 
lakes  at  the  surface,  as  in  the  interior  the  hollows  are  soon  filled 
with  water  vapor. 

(c)  Loss  of  a  Constituent.  —  A  loss  of  CO2  takes  place  in  mov- 
ing water  in  contact  with  air,  as  at  outlets  of  springs  or  rivers. 

(cT)  Solution  of  Another  Substance.  —  Solutions  saturated  with 
one  substance  can  dissolve  another,  but  a  saturated  complex  solu- 
tion contains  less  of  either  salt  than  when  saturated  by  it  alone. 
Hence  a  saturated  solution  coming  in  contact  with  a  new  sub- 
stance may  dissolve  some  of  it,  but  if  so  will  deposit  some  of  the 
substance  previously  in  solution. 

II.  Chemical  Reaction  or  Mutual  Exchange. 

If  a  solution  comes  into  contact  with  some  substance,  from  which 
by  chemical  exchange  a  less  soluble  compound  can  result,  a  pre- 
cipitation of  this  new  substance  will  take  place.  In  this  way,  espe- 
cially in  very  dilute  solutions  or  by  gradual  contact,  many  beautiful 
crystals  are  formed.  Very  often  the  reaction  can  be  traced  in 
pseudomorphs  and  altered  minerals. 

The  law  of  mass  action  rules,  that  is,  each  material  exerts  chemi- 
cal action  proportionate  to  its  mass.  Exactly  opposite  results  are 
obtainable;  for  instance,  BaCO3  with  sufficient  sulphate  solution 
is  all  changed  to  BaSO4  and  BaSO4  with  sufficient  carbonate 
solution  is  all  changed  to  BaCO3.  If  the  quantity  of  solution  is 
not  sufficient,  a  stage  is  reached  in  which  both  salts  are  simultane- 
ously in  solution.  Much  less  solution  is  needed  to  convert  the 
comparatively  easily  soluble  BaCO3  into  nearly  insoluble  BaSO4 
than  for  the  reverse  action. 

THE  MINERALS  DEPOSITED  BY  SPRINGS. 

The  water  emerging  at  a  spring  is  often  merely  rain  water 
which  has  followed  a  comparatively  short  course  through  the  soil 


200  DESCRIPTIVE  MINERALOGY. 

and  emerged  at  a  lower  elevation.  It  contains  little  more  than 
the  dissolved  gases  from  the  atmosphere.  In  other  springs  how- 
ever the  higher  temperatures  or  the  dissolved  constituents  show  a 
deeper  source.  In  rising,  the  pressure  and  therefore  the  solvent 
power  decrease,  and  loss  of  CO2,  evaporation  and  reactions  may  all 
tend  to  the  deposition  of  solids. 

The  usual  constituents  of  spring  waters  are  chlorides,  sulphates 
and  carbonates  of  the  alkalis  and  alkaline  earths,  free  silica,  phos- 
phates of  iron  or  aluminum,  and  alkaline  silicates.  All  of  these 
have  been  obtained  experimentally  by  treating  powdered  rocks 
with  water  containing  CO2. 

Carbonates  from  Spring  Waters. 

Hot  springs  often  deposit  calcite  or  aragonite  as  stalactites  or  if 
the  solution  fall  on  loose  sand  kernels  or  the  separation  is  upon 
some  nucleus  in  moving  water,  oolitic  deposits  result.  In  brooks 
and  rivers  a  compact,  calc  sinter  forms.  In  iron  mines  aragonite 
separates  as  "  flos  ferri."  Other  carbonates,  such  as  siderite,  hydro- 
zincite,  and  hydrodolomite  form  also.  The  cause  is  usually  loss 
of  CO2  by  diminished  pressure. 

Silica  from  Spring  Water. 

Massive  opal  is  precipitated  from  geysers  chiefly  by  organisms 
as  described  later.  At  other  times  quartz  or  chalcedony  is  de- 
posited, evidently  as  the  result  of  the  decomposition  of  a  silicate 
by  carbonated  water. 

Sulphur  and  Sulphides  from  Springs. 

Sulphur  springs  containing  either  H2S  or  some  sulphide  are  not 
rare.  At  Steamboat  Springs,  California,  the  emerging  hot  waters 
penetrate  a  clayey  paste  containing  grains  of  cinnabar ;  with  it  are 
alternate  beds  of  pyrite  and  chalcedony.  The  ascending  hot 
waters  contain  alkaline  carbonates  and  sulphides  with  an  excess  of 
CO2  and  H2S,  these  evidently  dissolved  the  silica  of  the  basalt  rock 
leaving  a  clay  behind.  By  decrease  of  pressure  the  silica  deposited 
as  chalcedony  and  at  the  same  time  the  iron  and  mercury  must 
have  been  thrown  down  as  sulphide.  Free  sulphur  is  also  present. 

Other  Deposits  from  Springs. 

Sassolite,  HBO3,  scorodite,  fluorite,  barite,  celestite,  the  alums, 
halloysite,  siderite,  and  limonite. 


OCCURRENCE  AND    ORIGIN  OF  MINERALS.  2OI 

THE   MINERALS    DEPOSITED    IN    VEINS. 

Those  clefts  and  cracks  in  the  earth  which  penetrate  to  great 
depths  and  frequently  occur  near  eruptive  rocks  or  near  springs 
containing  CO2  and  H2S,  contain  as  their  principal  minerals  quartz, 
barite,  calcite,  fluorite  and  the  ores.  Silicates  are  rare,  crystals  are 
frequent  and  the  minerals  are  deposited  on  the  walls  of  the  cleft, 
first  the  most  insoluble,  such  as  quartz,  then  barite,  calcite,  fluorite 
and  so  on,  usually  symmetrically  to  the  center  of  the  cleft. 

All  these  facts  accord  with  the  theory  that  these  vein  clefts  had 
not  a  free  outlet  to  the  surface  and  became  filled  with  water,  which, 
instead  of  moving  upward  rapidly  as  in  springs,  had  a  hardly  notice- 
able current  and  coming  from  below  would  contain  CO2  and  bicar- 
bonates  and  often  sulphides,  H2S,  and  sulphates. 

From  the  rocks  cut  by  the  vein  the  ground  water  may  be  assumed 
to  have  formed  concentrated  solutions  of  silicates,  which  reaching 
the  vein  would  meet  water  already  there  and  would  be  slowly 
diffused  in  this  vein  water  containing  CO2,  H,S,  bicarbonates,  etc. 
The  conditions  would  be  most  favorable  for  the  formation  of  crystals. 
Reactions  between  CO,  and  the  dissolved  silicates  would  form  quartz 
and  carbonates  and  but  little  silicate  while,  by  the  action  of  H2S  and 
dissolved  sulphides  on  the  metallic  compounds,  there  would  result 
insoluble  sulphides  of  heavy  metals  and  the  sulphates  would  cause 
barite.  The  most  insoluble  compounds  would  be  deposited  first. 

MINERALS  FORMED  BY  THE  GROUND  WATER  IN  THE  ROCK  MASS. 
The  action  of  the  "ground"  water  in  dissolving  the  minerals 
throughout  the  rock  mass  is  accompanied  by  new  formations  where- 
ever  the  necessary  solid,  liquid  or  gaseous  precipitant  is  encoun- 
tered. Solutions  from  some  vein  cleft  may  be  diffused  through  the 
pores  of  the  decomposing  rock  or  may  communicate  with  crevices 
and  penetrate  sediments  and  cause  therein  production  of  the  same 
minerals.  The  minerals  thus  produced  are  principally  calcite  and 
quartz  and  more  rarely  gypsum  or  sulphides,  such  as  cinnabar, 
pyrite,  sphalerite  or  chalcopyrite.  So  also  partially  altered  material 
and  pseudomorphs  may  be  found  through  the  mass,  and  entire 
rock  masses  may  be  altered  producing,  according  to  their  composi- 
tion, clays,  chlorites,  serpentines,  talcs,  calcite,  quartz,  limonite, 
epidote  and  the  micas. 

Certain  secondary  minerals  which  can  not  be  traced  to  the  deep  veins  are  evidently 
due  to  the  watery  solutions  which  have  formed  in  the  upper  portion  of  the  earth's  crust. 


202  DESCRIPTIVE   MIXERALOGY. 

The  minerals  are  either  those  of  the  adjacent  rock  or  their  components  are  derived  there- 
from. Beautiful  druses  of  brilliant  crystals  are  found  lining  cavities  and  clefts  in  the 
rocks,  and  in  the  hollows  due  to  gases  and  vapors  at  the  time  of  formation.  Often  two 
or  more  species  occur  in  symmetrical  layers  on  the  walls.  They  occur  more  frequently 
in  rocks  low  in  silica,  because  the  soluble  substances  necessary  to  their  formation  are 
more  plentiful.  The  more  common  species  are  quartz,  chalcedony,  calcite,  siderite, 
the  various  zeolites,  datolite,  prehnite,  barite,  delessite,  etc.  Here  belong  also  the  new 
formed  crystals  in  clay,  marl  or  sand  and  the  cementing  material  of  conglomerates  and 
sandstones. 

THE  MINERALS  FORMED  IN  OCEANS,  SEAS  AND  LAKES. 
Rivers  and  brooks  carry  to  the  seas  and  lakes  into  which  they 
empty,  mineral  fragments  in  suspension  which  are  mechanically  de- 
posited, and  substances  in  solution  which  by  concentration  and  re- 
actions form  minerals.  The  principal  constituents  are  sulphates, 
chlorides  and  carbonates  of  calcium,  magnesium  and  sodium.  The 
proportion  in  which  they  stand  is  very  different  in  the  rivers  and 
the  oceans. 

AVERAGE  OF  FIVE  GREAT  RIVERS.  OCEAN. 

Carbonates,  80  0.2 

Chlorides,       7  90 

Sulphates,     13  10 

The  proportion  of  dissolved  solids  in  the  ocean  is  only  33  to  37  in  the  1000.  Deep 
sea  dredgings  bring  to  light  principally  a  red  clay  containing  minute  crystals  of  a  rare 
zeolite  called  phillipsite,  nodules  of  hydrated  oxide  of  manganese  and  iron  and  some 
enstatite,  all  apparently  resulting  from  the  decomposition  of  a  lava. 

For  the  dissolved  constituents  to  separate  there  is  needed  a  con- 
centration of  the  solution,  that  is,  a  land-locked  basin  and  a  warm 
climate.  With  these  conditions  there  separate  various  minerals  ;  in 
order  generally  of  their  solubility,  but  thus  dependent  also  upon 
the  proportion  of  associates  and  the  temperature. 

The  Formation  *  of  the  Stassfurt  Salt  Deposit  as  a  Type. 
Five  regions  may  be  named  commencing  at  the  bottom. 

1.  The  Anhydrite  (CaSOJ  region,  composed  chiefly  of  rock 
salt,  but  with  strings  of  anhydrite  varying  from  4  to  9  per  cent,  of 
all.      Thickness  330  meters. 

2.  The  Polyhalite  (2CaSO4.MgSO4.K2SO4.  2H2O)  region,  com- 
posed of  halite,  91.2;  anhydrite,  0.7;    polyhalite,  6.2;  tachydrite, 
1.5  per  cent.      Thickness  62  meters. 

3.  The  Kieserite  (MgSO4.H2O)  region,  composed  of  halite,  65.0  ; 

*  Condensed  principally  from  Braun's  Chemische  Mine^alogie,  pp.  340-346. 


OCCURRENCE  AND    ORIGIN  OF  MINERALS.  203 

kieserite,  17  ;  carnallite,  13  ;  tachydrite,  3.0;  anhydrite,  2  per  cent. 
Thickness  56  meters. 

4.  The  Carnallite  (KCl.MgCl2.6H2O)  region,  composed  of  carnal- 
lite,    55.0;  kieserite,  16.9;  halite,   25.0;  tachydrite,  4.0  percent. 
Thickness  42  meters,  but  in  successive  thin  layers  in  the  order 
named.     Here  occur  also  a  large  number  of  secondary  minerals. 

5.  The  Kainite  (MgSO4.KC1.3H2O),  a  secondary  formation  on 
the  rise  of  the  strata  and  due  to  the  action  of  a  limited  quantity  of 
water  on  kieserite  and  carnallite.      Above  these  there  is  a  later 
formation  of  salt  clay  and  successive  layers  of  anhydrite,  halite 
and  thin  layers  of  polyhalite.     Thickness,  40  to  90  meters. 

The  primary  minerals  were  probably  only  anhydrite,  halite, 
polyhalite,  kieserite,  carnallite,  possibly  part  of  sylvite  and  boracite, 
the  less  soluble  separating  first. 

Theory  as  to  Formation.  —  Probably  a  basin  of  the  sea  was  sepa- 
rated from  the  ocean  by  a  bar,  gradually  concentrated  by  evapora- 
tion but  with  constant  addition  of  more  sea  water.  There  would 
be  a  separation  first  of  gypsum  and  halite,  then,  as  the  magnesia 
contents  increased,  gypsum  would  be  hindered  and  anhydrite 
formed.  In  time  there  would  be  at  the  bottom  of  the  basin  a 
strong  solution  rich  in  magnesia  salts,  while  above,  the  constant 
inflow  and  overflow  at  the  bar  would  result  in  a  relatively  dilute 
solution. 

At  a  later  date  the  raising  of  the  bar  apparently  converted  the 
basin  into  a  salt  lake  which  evaporation  and  the  gradual  separation 
of  the  halite  converted  into  a  supersaturated  solution  of  magnesium 
sulphate  from  which  kieserite  crystallized.  The  mother  liquor 
then  evidently  consisted  of  an  excess  of  MgCl2  with  KC1,  for  only 
then,  in  experiments,  will  the  double  salt,  carnallite,  form. 

Other  reactions  produced  secondary  minerals,  as  described  by 

Braun. 

MINERALS  FORMED  IN  SODA  LAKES. 

In  certain  lakes,  carbonates,  borates  and  sulphates  predominate. 
Near  Laramie,  Wyoming,  are  deposits  20  to  30  feet  deep,  prin- 
cipally of  sodium  sulphate,  mirabilite,  Na.,SO4  -f  ioH2O. 

The  same  mineral  separates  from  the  Great  Salt  Lake,  when  the 
temperature  is  low,  and  is  heaped  up  by  the  waves  on  the  beaches 
where,  if  not  collected,  it  redissolves  as  soon  as  the  temperature 
rises. 

In  other  lakes  and  pools  and  in  a  crust  resulting  from  their 


204  DESCRIPTIVE  MINERALOGY. 

evaporation  there  is  found  the  mineral  trona,  Na2CO3.NaHCO3. 
2H2O ;  and  less  frequently  two  other  carbonates,  natron  and 
thermonatrite. 

MINERALS  FORMED  IN  BORAX  LAKES  AND  LAGOONS. 
Borapc  lakes  and  lagoons  are  found  in  regions  of  volcanic  activity 
and  have  probably  received  boric  acid  from  hot  springs.  Accord- 
ing to  their  other  contents  there  may  separate  sassolite,  HBO3, 
borax,  colemanite  or  other  borates.  If  sulphates  are  present  they 
will  also  separate. 

Borax  Lake,  Cal.,  for  instance,  furnishes  anhydrite,  calcite,  celestite,  cerargyrite, 
colemanite,  dolomite,  embolite,  gaylussite,  glauberite,  gold,  halite,  natron,  soda-nitre, 
sulphur,  thenardite,  trona,  hanksite  and  sulphohalite. 

MINERAL  FORMATION  BY  ORGANISMS. 

A  great  portion  of  the  solid  earth  is  due  to  lower  forms  of  animal 
and  vegetable  life.  Corals,  mussels,  echinoderms,  etc.,  in  some 
way  take  calcium  *  from  sea  water  and  build  with  it  shells  and 
frame  works,  chiefly  of  CaCO3.  Plant  organisms,  algae,  nullipores, 
etc.,  precipitate  CaCO3,  which  in  this  way  forms  reefs  and  banks  of 
limestone. 

The  change  to  crystalline  limestone  is  due  chiefly  to  carbonated 
water,  sometimes  assisted  by  heat  and  pressure,  which  dissolve  the 
amorphous  material  and  at  the  same  time  precipitate  the  less  soluble 
crystalline  material.  Fresh-water  limestones  (calc-tufa  or  traver- 
tine) are  formed  by  the  precipitation  of  CaCO3  from  springs,  rivers 
and  brooks  rich  in  calcium  bicarbonate,  by  algae,  moss  and  other 
plants  which,  needing  CO2  for  nourishment,  take  it,  thereby  precipi- 
tating upon  them  the  insoluble  carbonate  and  dying,  except  at  the 
top,  gradually  form  a  spongy  mass  of  calcite  or  aragonite. 

Dolomite,  CaCO3.MgCO3,  in  mighty  mountain  ranges  is  formed 
from  organically  precipitated  CaCO3  containing  much  less  than  the 
requisite  per  cent,  of  MgCO3.  Most  coral  has  less  than  one  per  cent, 
but  certain  lithothamniens  often  found  on  the  outside  of  coral  reefs 
contain  up  to  13  per  cent.  MgCO3.  One  explanation  of  the  enrich- 
ment is  that  the  CaCO3  of  corals  is  aragonite,  since  by  experi- 


*  The  Ca  must  be  largely  obtained  from  CaSO4  as  the  ocean  contains  only  a  little 
bicarbonate.  One  assumption  is  that  plant  organisms  decompose  the  CaSO4  and  that 
they  are  eaten  by  animals.  Another,  that  it  is  decomposed  directly  in  the  animal. 
Organisms  develop  (NH4)2CO,  which  would  precipitate  the  lime  as  carbonate. 


OCCURRENCE  AND    ORIGIN  OF  MINERALS.  205 

ment  in  concentrated  salt  solution  about  42  per  cent,  of  aragonite 
is  changed  to  MgCO3  by  contact  with  MgSO4  at  91°  C.,  giving 
essentially  dolomite.  In  a  closed  sea  basin  in  a  warm  climate  these 
conditions  would  prevail. 

Silica  is  taken  from  ocean  water  by  sponges,  radiolaria,  etc., 
and  forms  banks  of  hornstone.  Diatoms  in  marshes  form  siliceous 
coatings  and  these  yield  great  beds  of  soluble  silica  (diatomaceous 
earth).  Algae  in  hot  springs  precipitate  geyserite. 

Sulphur  is  separated  from  sulphates  by  certain  algae  and  bacteria, 
and  from  sulphates  by  decomposing  organic  matter. 

Limonite  (bog  ore)  is  in  part  due  to  one  of  the  algae  which  builds 
iron  into  its  structure,  but  it  is  most  of  it  due  to  the  acids  resulting 
from  the  decomposition  of  plants  which  dissolve  iron  from  the  soil 
and  the  solution  later  decomposes  into  limonite,  CO2  and  H2O. 

Pyrite,  marcasite  and  some  other  sulphides  are  precipitated  from 
solutions  by  decomposing  organic  matter. 

Nitre  forms  as  the  result  of  a  fermentation  involving  bacteria. 


Chemical  and  physical  changes  take  place  as  the  result  of  light, 
some  precipitations  are  electrolytic  and  the  absorbing  or  losing 
of  water  may  effect  an  entire  change  in  the  structure  and  nature 
of  a  species. 


CHAPTER   XXI. 


THE    IRON    MINERALS. 


THE  minerals  described  are  : 


Metal 

Iron 

Fe 

Sulphides 

Pyrrhotite 

FenSn+1 

Hexagonal 

Pyrite 

FeS2 

Isometric 

Marcasite 

FeS2 

Orthorhombic 

Sulpharsenide 

Arsenopyrite 

FeAsS 

" 

Arsenide 

Leucopyrite 

Fe3As4 

" 

Oxides 

Magnetite 

Fe304 

Isometric 

Franklinite 

(Fe.Mn.Zn)3O4 

" 

Hematite 

FeA 

Hexagonal 

Ilmenite 

(Fe.Ti)2Os 

" 

Hydroxides 

Turgite 

Fe405(OH)a 

Coethite 

FeO(OH) 

Orthorhombic 

Limonite 

Fe2(OH)6.Fe203 

Sulphates 

Copiapite 

Fe2(FeOH)2(S04)5H 

-l8H2O  Monoclinic 

Melanterite 

FeS04  +  7H20 

" 

Phosphate 

Vivianite 

Fe,(P04)2  +  8H20 

" 

Carbonate 

Siderite 

FeCO3 

Hexagonal 

Chr  ornate 

Chromite 

FeCr.,O4 

Isometric 

Columbate 

Columbite 

Fe(Cb03), 

Orthorhombic 

Tungstate 

Wolframite 

(FeMn)WO4 

Monoclinic 

Economic  Importance. 

The  iron  minerals  have  important  and  varied  uses,  which  may 
briefly  be  described  under  the  following  heads  : 

I.  —  In  natural  state. 
II.  —  For  extraction  of  metal  (ores  of  iron). 

III.  —  For  extraction  of  acid  constituents. 

IV.  —  For  extraction  of  included  metals. 

I.  —  Uses  in  Natural  State. 

In  1902  the  production  of  ocher,  umber  and  sienna  and  natural 
oxide  paints  was  55,320  short  tons.*  Limonite  and  hematite  are 
the  principal  natural  oxides  ground  for  paint. 

II.  —  Minerals  Used  as  Ores  of  Iron. 

In  the  United  States  the  minerals  smelted  for  iron  are,  in  order 


*  Mineral  Industry,  1902. 


206 


THE  IRON  MINERALS.  2O? 

of  quantity  used,  *  hematite,  limonite,  magnetite,  and  siderite. 
Goethite  and  turgite  are  commercially  included  with  limonite 
under  the  name  brown  hematite,  and  some  ilmenite  is  smelted 
with  other  ores.  The  residues  from  the  roasting  of  pyrites  are 
sometimes  used  as  a  source  of  iron,  but  not  in  this  country. 

In  1903  the  United  States  produced  31,605,550!  long  tons  of 
iron  ore,  about  three  quarters  of  which  came  from  the  Lake  Su- 
perior region  of  Wisconsin  and  Minnesota,  and  about  one  sixth 
came  from  the  Southern  States. 

The  greater  portion  of  the  iron  ore  mined  in  the  world  each  year 
is  converted  into  pig  iron,  of  which  44,558,000  tons  were  produced 
in  1902.  That  is,  the  ore  is  deprived  of  its  oxygen  by  the  action 
of  incandescent  carbon  and  the  hot  reducing  gases  resulting  from 
its  combustion,  and  becomes  a  liquid  mass  of  metallic  iron,  com- 
bined and  mixed  with  a  little  carbon,  silicon,  phosphorus,  sulphur 
and  other  impurities.  The  furnace  used  is  a  vertical  shaft,  every- 
where circular  in  horizontal  section,  but  usually  widening  from  the 
top  downwards  to  a  certain  level,  and  then  again  narrowing  to  the 
hearth.  Hot  air  is  forced  into  the  furnace  through  nozzles  called 
tuyeres,  entering  just  above  the  hearth. 

The  ore  and  fuel  are  analyzed  and  some  flux  is  added,  which, 
when  combined  with  the  ash  of  the  fuel  and  the  foreign  ingredi- 
ents of  the  ore,  forms  a  definite  silicate  of  known  fusibility,  called 
the  slag.  The  temperature  of  the  furnace  differs  at  different  levels, 
but  is  practically  the  same  at  all  times  at 'any  one  level. 

The  ore,  charged  at  the  top,  in  alternate  layers  with  fuel  and 
flux,  passes  through  zones  of  different  temperature  as  it  descends, 
and  is  reduced,  carburized,  fused,  and  flows  into  the  hearth.  The 
slag  forms  in  a  definite  zone  after  the  complete  reduction  of  the 
iron,  and  falls  also  to  the  hearth,  but,  being  lighter,  floats  on  the 
melted  iron  until  drawn  off.  From  time  to  time  the  metal  is  run 
out  into  sand  moulds,  forming  the  pigs  or  pig  iron,  of  which  17,- 
942,8404]  long  tons  were  produced  in  the  United  States  in  1903. 

This  pig  iron,  by  various  processes,  is  converted  into  wrought 
iron,  cast  iron  and  steel. 

*John  Birkinbine,  in  Mineral  Resources  of  United  States,  1902,  p.  42,  gives  as 
amounts  mined  for  one  year;  Hematite,  30,532,149  tons  or  85.9  per  cent.;  limonite 
and  goethite,  3,305,484  tons  or  9.6  per  cent.;  magnetite,  1, 688,860  tons  or  4.7  per 
cent;  siderite,  27,642  tons. 

f  Engineering  and  Mining  Journal,  1904,  p.  46. 

\Loc.  cit. 


208  DESCRIPTIVE  MINERALOGY. 

The  mineral  franklinite,  after  treatment  for  zinc,  and  certain  man- 
ganiferous  hematites  and  siderites,  are  smelted,  for  spiegeleisen,  an 
alloy  of  iron  and  manganese,  used  as  a  source  of  carbon  and  man- 
ganese in  the  manufacture  of  steel. 

III.  —  Minerals  Used  for  Extraction  of  Acid  Constituents. 

(a)  FOR  SULPHUR.  —  Pyrite,  and,  to  a  less  extent,  marcasite  and 
pyrrhotite,  are  very  extensively  used  in  the  manufacture  of  sul- 
phuric acid.  In  1903,  580,000  tons  were  so  used  in  the  United 
States.  The  sulphides  are  burned  in  furnaces  with  grates,  and  the 
gases  are  converted  into  sulphuric  acid.  The  residues,  in  addition 
to  iron,  frequently  contain  copper,  nickel  or  gold,  and  these  are 
usually  extracted  later. 

(£)  FOR  ARSENIC.  —  The  mineral  arsenopyrite  is  the  chief  source 
of  arsenic.  See  p.  270. 

(<:)  FOR  CHROMIUM.  —  Practically  all  the  chromium  compounds 
derive  their  chromium  from  the  mineral  chromite,  very  little  of 
which  is  now  mined  in  the  United  States.  The  most  important 
compounds  manufactered  are  :  potassium  bichromate,  used  in  calico 
printing,  oxidizing  rubber,  bleaching  indigo  and  in  manufacturing 
chrome  paints  and  matches ;  potassium  chromate  used  in  the 
manufacture  of  aniline  colors,  etc.,  and  ferro-chromium,  which 
added  to  steel  produces  the  tough  alloy  known  as  chrome-steel. 

(d)  FOR  TUNGSTEN.  —  Tungsten  and  the  tungstates  are  extracted 
from  wolframite  and  scheelite.  The  world's  product  is  not  more 
than  600  to  700  tons,  and  is  chiefly  employed  in  the  manufacture 
of  crude  tungsten  for  self-hardening  tungsten  steel  and  sodium 
tungstate  for  rendering  fabrics  non-inflammable. 

IV.  —  Included  Metals. 

(a)  GOLD  AND  SILVER.  —  Both  pyrite  and  arsenopyrite  frequently 
carry  gold  and  a  little  silver,  which  may  be  extracted  either  directly 
by  stamping  and  amalgamation  or,  more  completely,  by  treatment 
of  the  roasted  residues  with  chlorine  or  potassium  cyanide  solution. 

(£)  NICKEL.  —  Pyrrhotite  frequently  carries  nickel,  and  in  1898 
about  2,700  tons  of  nickel  were  extracted  from  the  pyrrhotite  of 
Sudbury,  Ontario. 

IRON. 

COMPOSITION.  —  Fe  with  some  Ni,  Cr,  Co,  Mn. 

GENERAL  DESCRIPTION.  —  Masses  and  imbedded  particles  of  white  to  gray  metal, 
resembling  manufactured  iron.  Many  meteorites  are  alloys  of  nickel  and  iron  and 


THE  IRON  MINERALS. 


209 


usually,  when  polished  and  etched  by  dilute  acid,  exhibit  lines  or  bands,  due  to  a  crys- 
talline arrangement  of  alloys  of  different  proportion  of  Fe  to  Ni.  Figs:  309,  310. 

PHYSICAL  CHARACTERS.  —  Opaque.  Lustre,  metallic.  Color,  steel-gray  to  iron- 
black.  Streak,  metallic  gray.  H.,  4  to  5.  Sp.  gr.,  7.3  to  7.8.  Tough  and  malle- 
able. Fracture,  hackly. 

BEF6RE  BLOWPIPE,  ETC.  —  Infusible.  Soluble  in  acids.  In  borax  or  salt  of  phos- 
phorus, reacts  only  for  iron. 


FIG.  309. 


FIG.  310. 


Sections  of  Iron  Meteorites  Etched  with  Acid. 

REMARKS. — Occurs  in  large  masses  on  Disco  Island,  Greenland,  and  sparingly  in 
some  basalts,  pyrite  nodules,  etc.,  and  locally  reduced  by  heat  from  the  carbonate. 
Also  found  in  most  meteorites  either  as  chief  constituent  or  as  a  spongy  matrix  or  in 
disseminated  grains. 

PYRRHOTITE. — Magnetic  Pyrites,  Mundic. 

COMPOSITION. — FenSn  +  x.  Fe6S7  to  FeuS12,  with  frequently  small 
percentages  of  cobalt  or  nickel. 

GENERAL  DESCRIPTION. — Usually  a  massive  bronze  metallic  min- 
eral, which  is  attracted  by  the  magnet  and  can  be  scratched  with 
a  knife.  Sometimes  occurs  in  tabular  hexagonal  crystals. 

Physical  Characters.     H.,  3.5  to  4.5.     Sp.  gr.,  4.5  to  4.6. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  grayish-black.  TENACITY,  brittle. 

COLOR,  bronze-yellow  to  bronze-red,  but  subject  to  tarnish. 
Attracted  by  the  magnet. 

BEFORE  BLOWPIPE,  ETC. — Fuses  readily  on  charcoal  to  a  black 
magnetic  mass,  evolves  fumes  of  sulphur  dioxide,  but  does  not  take 
fire.  In  closed  tube,  yields  a  little  sulphur.  In  open  tube,  gives 
fumes  of  sulphur  dioxide.  Soluble  in  hydrochloric  acid,  with 
evolution  of  hydrogen  sulphide  and  residue  of  sulphur. 

SIMILAR  SPECIES. — Pyrrhotite  resembles  pyrite,  bornite  and  nic- 
colite  at  times,  but  differs  in  being  attracted  by  the  magnet  and  by 
its  bronze  color  on  fresh  fracture. 
14 


210 


DESCRIPTIVE  MINERALOGY. 


•>  REMARKS. — Pyrrhotite  is  found  in  gabbros  and  ^chists  and  occasionally  in  the 
older  eruptive  rocks,  also  frequently  in  meteorites.  It  alters  to  pyrite,  limonite  and 
siderite. 

Immense  quantities  are  found  at  Strafford  and  Ely,  Vermont ;  Sudbury,  Canada, 
and  Lancaster  Gap,  Pennsylvania.  The  last  two  deposits  are  nickeliferous,  and  are 
mined  for  this  metal.  Smaller  beds  are  common. 

USES. — It  is  one  of  the  chief  ores  of  nickel,  probably  from  in- 
cluded minerals;  and  to  some  extent  is  an  ore  of  sulphur. 


PYRITE.— Iron  Pyrites,  Fool's  Gold. 

COMPOSITION. — FeS2  (Fe  46.7,  S  53.3  per  cent.),  often  contain- 
ing small  amounts  of  Cu,  As,  Ni,  Co,  Au. 

GENERAL  DESCRIPTION. — A  brass  -  colored,  metallic  mineral, 
frequently  in  cubic  or  other  isometric  crystals  or  in  crystalline 
masses,  which  may  be  any  shape,  as  botryoidal,  globular,  stalac- 
titic,  etc.  Less  frequently  in  non-crystalline  masses. 

FIG.  311. 


Pyrite  in  Schist,  Lourdes.     After  Lacroix. 


CRYSTALLIZATION.  —  Isometric,  class  of  diploid,  p.  59.  Most 
common  forms  are  cube  a,  Fig.  312,  and  pyritohedron  e,  Fig.  313, 
a :  2a :  oo  a  ;  { 2 10}  or  combinations  of  these,  Fig.  315.  The  octa- 
hedron also  occurs  alone,  Fig.  314,  or  in  combination  with  a  and 


THE   IRON  MINERALS. 


211 


e,  Figs.  316,  317,  318,  and  the  diploid  s  =  (a :  j  a :  3^)  ;   {321}  is 
not  rare  in  combinations,  Fig.  319,  320. 

The  faces  of  the  cube  and  pyritohedron  are  frequently  striated 
in  one  direction  parallel  to  intersections  of  these  two  forms.  See 
Fig.  251. 


FIG.  312. 


FIG.  313- 


FIG.  314. 


FIG.  315. 


FIG.  316. 


FIG.  317. 


FIG.  318. 


Physical  Characters.     H.,  6  to  6.5.     Sp.  gr.,  4.9  to  5.2. 

LUSTER,  metallic.  OPAQUE. 

STREAK,  greenish-black.  TENACITY,  brittle. 

COLOR,  pale  to  full  brass-yellow  and  brown  from  tarnish. 
CLEAVAGE,  imperfect  cubic. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal,  takes  fire  and  burns  with  a 
blue  flame,  giving  off  fumes  of  sulphur  dioxide,  and  leaving  a  mag- 
netic residue  which,  like  pyrrhotite,  dissolves  in  hydrochloric  acid 
with  evolution  of  hydrogen  sulphide.  In  closed  tube,  gives  a 


212  DESCRIPTIVE  MINERALOGY. 

sulphur  deposit.     Insoluble  in  hydrochloric  acid,  but  soluble  in 
nitric  acid  with  separation  of  sulphur. 

SIMILAR  SPECIES. — Pyrite  is  harder  than  chalcopyrite,  pyrrho- 
tite,  or  gold.  It  differs  from  gold,  also,  in  color,  streak,  and  brit- 
tleness. 

REMARKS. — Pyrite  is  being  formed  to-day  by  the  action  of  the  hydrogen  sulphide 
of  thermal  springs  upon  soluble  iron  salts.  It  has  been  developed  in  many  rocks  by 
the  action  of  hot  water  on  iron  salts  in  the  presence  of  decomposing  organic  matter. 
It  may  be,  also,  of  igneous  origin.  Pyrite  is  found  in  rocks  of  all  ages,  associated 
with  other  metallic  sulphides  and  with  oxides  of  iron.  In  compact  specimens  it  is  not 
easily  altered,  but  granular  masses  readily  oxidize  and  are  decomposed,  forming  sul- 
phate of  iron  and  sulphuric  acid,  thus  acting  as  a  vigorous  agent  in  the  decomposition 
of  rocks.  The  final  results  are  usually  limonite  and  sulphates  of  calcium,  sodium, 
magnesium,  etc.  Few  minerals  are  of  such  general  or  wide-spread  occurrence.  The 
most  celebrated  locality  is  the  Rio  Tinto  region,  in  Spain,  from  which  immense  quan- 
tities of  a  gold-  and  copper-bearing  pyrite  are  annually  procured.  The  largest  deposits 
worked  in  the  United  States  are  at  Rowe,  Mass. ;  Hermon,  N.  Y. ;  and  at  several 
localities  in  Virginia.  Innumerable  large  deposits  are  known. 

USES. — Pyrite  is  burned,  for  the  manufacture  of  sulphuric  acid, 
in  enormous  quantities.  Pyrite  containing  copper  or  gold  is  some- 
times treated  for  these  metals,  but,  the  treatment  is  frequently  pre- 
ceded by  a  burning  for  sulphuric  acid.  The  use  of  pyrite  for  the 
manufacture  of  copperas  has  been  superseded  by  a  process  of  gal- 
vanizing iron  in  which  copperas  is  a  by-product. 

MARCASITE— White  Iron  Pyrites. 

COMPOSITION. — FeS,,  as  in  pyrite. 

GENERAL  DESCRIPTION. — Ferric  sulphide  is  dimorphous.  Mar- 
casite  differs  from  pyrite  in  crystalline  form,  and  in  little  else. 
It  occurs  in  orthorhombic  forms,  and  in  crystalline  masses.  The 
compound  crystals  have  given  rise  to  such  names  as  cockscomb 

FIG?  321.  FIG.  323. 


FIG.  322. 

pyrites,  spear  pyrites,  etc.,  from  their  resemblance  to  these  objects. 
Often,  with  radiated  structure.  Color  on  fresh  fracture  is  usually 
whiter  than  in  pyrite. 


THE  IRON  MINERALS.  21$ 

CRYSTALLIZATION. —  Orthorhombic,  a :  ~b\  c  =  0.7662 :  i :  1.2342. 
Crystals  usually  tabular  parallel  to  base. 

Simple  forms  show  unit  prism  m,  basal  pinacoid  c  and  often  one 
or  more  brachy  domes  as  g=  (corf:  b\  ^l)  ;  [013].  Compound 
"fivelings"  with  twin  plane  m,  Figs.  323  and  324,  are  frequent. 

Supplement  angles  are  mm  =  74°  55',  eg  =  22°  21'. 

FIG.  324. 


Marcasite  Twin  Crystal.     After  Lacroix. 

Physical  Characters.     H.,  6  to  6.5.     Sp.  gr.,  4.6  to  4.9. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  nearly  black.  TENACITY,  brittle. 

COLOR,  pale  brass-yellow,  darker  after  exposure. 
CLEAVAGE,  imperfect  prismatic  (angle  of  105°  5')- 

BEFORE  BLOWPIPE,  ETC. — As  for  pyrite. 

SIMILAR  SPECIES. — As  for  pyrite,  from  which  it  is  only  distin- 
guishable by  crystalline  form,  cleavage,  and,  to  a  slight  degree,  by 
lighter  color. 

REMARKS. — Marcasite  is  more  readily  decomposed  than  pyrite,  and  is,  therefore,  an 
even  less  desirable  constituent  in  building  material,  etc.  It  is  found  at  Cummington, 
Mass.;  Warwick,  N.  Y. ;  Joplin,  Mo. ;  Haverhill,  N.  H.;  and  in  many  other  localities 
and  is  usually  mistaken  for  pyrite. 

USES,  are  the  same  as  for  pyrite. 


214 


DESCRIPTIVE  MINERALOGY. 


ARSENOPYRITE.— Mispickel. 

COMPOSITION. — FeAsS.  (Fe  34.4,  As  46.0,  S  19.6  per  cent.) 
sometimes  with  replacement  of  iron  by  cobalt,  or  arsenic  by  anti- 
mony in  part. 

GENERAL  DESCRIPTION. — Silver  white  to  gray  mineral  with 
metallic  lustre.  Usually  compact  or  in  granular  masses  or  dis- 
seminated grains.  Less  frequently  in  orthorhombic  crystals  or 

columnar. 

FIG.  325. 


Arsenopyrite,  Freiberg,  Saxony.     N.  Y.  State  Museum. 

CRYSTALLIZATION.  —  Orthorhombic  d\b\c=  0.677  :  i  :  1.188. 
Common   forms,   unit    prism  m    combined    with  a    brachy  dome 


FIG.  326. 


FIG.  327. 


FIG.  328. 


either  d=  (aoa  :  b  :  c] ;  {on}  orf  =  (cod:  b  :  \c]\  {014}.    Crossed 
twins,  Fig.  328,  occur  and  fivelings,  as  in  Fig.  323  of  marcasite. 
Supplement  angles  ;//;//  =  68°  13',  dd  =  99°  50',  ee  =  33°  05'. 


THE  IRON  MINERALS.  21$ 

Physical  Characters.  H.  5.5  to  6.  Sp.  Gr.,  6  to  6.2. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  grayish-black.  TENACITY,  brittle. 

COLOR,  silver  white  to  steel  gray. 
CLEAVAGE,  prismatic  (i  1 1°  47). 

BEFORE  BLOWPIPE,  ETC. — In  closed  tube  yields  a  red  sublimate, 
yellow  when  cold.  On  charcoal  yields  abundant  white  fumes  and 
arsenical  odor  and  coating  and  fuses  to  a  magnetic  globule.  After 
short  treatment  the  residue  is  soluble  in  hydrochloric  acid  with 
evolution  of  hydrogen  sulphide  and  precipitation  of  the  yellow  sul- 
phide of  arsenic.  The  residue  may  react  for  cobalt.  Insoluble  in 
hydrochloric  acid.  Soluble  in  nitric  acid  with  separation  of  sulphur. 

SIMILAR  SPECIES. — Massive  varieties  of  the  metallic  cobalt  min- 
erals and  varieties  of  leucopyrite  resemble  arsenopyrite  and  are 
only  safely  distinguished  by  blowpipe  tests.  Smaltite  when  mas- 
sive can  be  distinguished  from  cobaltiferous  arsenopyrite  only  by 
its  slight  reaction  with  hydrochloric  acid  after  fusion. 

REMARKS. — Arsenopyrite  is  found  chiefly  in  crystalline  rocks  with  other  metallic 
sulphides  and  arsenides.  Throughout  the  Rocky  Mountains  it  is  a  common  mineral 
and  frequently  auriferous.  A  large  deposit  at  Deloro,  Canada,  is  mined  for  both 
arsenic  and  gold.  The  arsenopyrite  found  in  New  England  usually  contains  cobalt. 

USES. — Arsenopyrite  is  the  source  of  most  of  the  arsenic  of 
commerce,  and  occasionally  contains  enough  gold  or  cobalt  to 
pay  for  extraction. 

LEUCOPYRITE.— Lollingite. 

COMPOSITION.— Fe3Asi  to  FeAs2  sometimes  with  Co,  Ni,  Au  or  S.    ' 

GENERAL  DESCRIPTION. — Massive  silver-white  or  gray  metallic  mineral  some* 
times  occurring  in  orthorhombic  crystals,  closely  agreeing  in  angles  with  crystals  of 
arsenopyrite.  c 

PHYSICAL  CHARACTERS. — Opaque.  Lustre,  metallic.  Color,  silver-white  or  "gray. 
Streak,  grayish-black.  H.  =  5  to  5.5.  Sp.  gr.,  7  to  7.4.  Brittle.  Cleavage,  basal. 

BEFORE  BLOWPIPE,  ETC. — Like  arsenopyrite,  except  that  sulphur  reactions  are  less 
pronounced  or  do  not  appear  at  all. 

MAGNETITE.— Lodestone,  Magnetic  Iron  Ore. 

COMPOSITION. — Fe3O4  (Fe,  72.4  per  cent.)  often  contains  Ti,  Mfj. 

GENERAL  DESCRIPTION. — A  black  mineral  with  black  streak  and 
metallic  lustre,  strongly  attracted  by  the  magnet  and  occurring  in 
all  conditions  from  loose  sand  to  compact  coarse  or  fine  grained 
masses. 


216 


DESCRIPTIVE  MINERAL  OGY. 


CRYSTALLIZATION.  —  Isometric,  usually  octahedra,  Fig.  329,  or 
loosely  coherent  masses  of  imperfect  crystals,  see  Fig.  268.  Some- 
times the  dodecahedron  d,  Fig.  330,  or  a  combination  of  these, 


FIG.  329. 


FIG.  330. 


FIG.  331. 


Fig.  333,  or  more  rarely  with  the  angles  modified  by  the  trapezohe- 
dron  o  =  (a  :  $a  :  30) ;    {311}.      Fig.  331. 

Twinning  parallel  to  an  octahedral  face  occurs,  sometimes  shown 
by  striations  upon  the  octahedral  faces,  as  in  Fig.  250. 

FIG.  332. 


Magnetite  in  Schist,  Geikie. 

Physical  Characters.     H.,  5.5  to  6.5.     Sp.  gr.,  4.9  to  5.2. 

LUSTRE,  metallic  to  submetallic.  OPAQUE. 

COLOR  and  STREAK,  black.  TENACITY,  brittle. 

Strongly  attracted  by  magnet  and  sometimes  itself  a  magnet 
(lodestone).  Breaks  parallel  to  octahedron. 

BEFORE  BLOWPIPE,  ETC. — Fusible  with  difficulty  in  the  reduc- 
ing flame.  Soluble  in  powder  in  hydrochloric  but  not  in  nitric 
acid. 

SIMILAR  SPECIES. — No  other  black  mineral  is  strongly  attracted 
by  the  magnet. 

REMARKS. — Magnetite  occurs  chiefly  in  crystalline  metamorphic  rocks  and  in  erup- 
tive rocks  partly  derived  from  silicates  containing  iron.  It  is  little  altered  by  expo- 
sure but  organic  matter  reduces  it  to  ferrous  oxide  which  by  oxidation  becomes  hema- 
tite, Fe2O8. 


THE  IRON  MINERALS.  21 7 

Tt  makes  up  about  12  per  cent,  of  tne  iron  ore  mined  in  America,  being  obtained 
especially  from  the  States  of  Pennsylvania,  New  York,  New  Jersey  and  Michigan. 
Smaller  amounts  are  obtained  elsewhere  and  it  is  present  in  many  localities.  In  this 
country,  lodestones  are  obtained  mainly  from  Magnet  Cove,  Ark.  Whole  mountains 
are  made  up  of  this  mineral  in  Sweden  and  it  is  practically  the  only  iron- ore  mined  in 
that  country. 

USES.  —  It  is  an  important  iron  ore  highly  valued  for  its  purity. 

FRANKLINITE. 

COMPOSITION.  —  (Fe.Mn.Zn)  (Fe.Mn)2O4. 

GENERAL  DESCRIPTION.  —  A  black  mineral  re- 
sembling magnetite.  Occurs  in  compact  masses, 
rounded  grains  and  octahedral  crystals.  Only 
slightly  magnetic  and  generally  with  brown 
streak.  The  red  zincite  and  yellow  to  green 
willemite  are  frequent  associates.  The  crystals 
are  modified  octahedrons  rarely  sharp  cut  as  in  magnetite. 

Physical  Characters.  —  H.,  6  to  6.5. .   Sp.  Gr.,  5  to  5.2. 

LUSTRE,  metallic  or  dull.  OPAQUE. 

STREAK,  brown  to  black.  TENACITY,  brittle. 

COLOR,  black.  Breaks  parallel  to  octahedron. 

Slightly  magnetic  at  times. 

BEFORE  BLOWPIPE,  ETC. — Infusible.  On  charcoal  with  soda 
gives  white  coat  of  zinc  oxide.  In  beads  gives  manganese  reaction. 
Slowly  soluble  in  hydrochloric  acid  with  evolution  of  some  chlorine. 

SIMILAR  SPECIES. — Distinguished  from  magnetite  and  chromite 
by  bead  tests  and  associates. 

REMARKS.— The  only  noteworthy  locality  is  that  in  the  vicinity  of  Franklin  Fur- 
nace, New  Jersey.  Here,  however,  the  deposit  is  large  and  has  been  extensively 
developed. 

USES. — The  zinc  is  recovered  as  zinc  white  and  the  residue  is 
smelted  for  spiegeleisen  an  alloy  of  iron  and  manganese  used  in 
steel  manufacture.  Franklinite  has  also  been  ground  for  a  dark 
paint. 

HEMATITE. — Specular  Iron,  Red  Iron  Ore. 

COMPOSITION. — Fe2O3,  (Fe  70  per  cent.),  often  with  SiO2l  MgO, 
etc.,  as  impurities. 

GENERAL  DESCRIPTION. — Occurs  in  masses  varying  from  bril- 
liant black  metallic  to  blackish  red  and  brick  red  with  little  lustre. 


218 


DESCRIPTIVE  MINERAL  OG  Y. 


The  black  is  frequently  crystallized,  usually  in  thin  tabular  crys- 
tals set  on  edge  in  parallel  position,  less  frequently  in  larger  highly 
modified  forms  and  finally  in  scale-like  to  micaceous  masses.  The 
red  varieties  vary  from  compact  columnar,  radiated  and  kidney- 
shaped  masses  to  loose  earthy  red  material.  In  all  varieties  the 
streak  is  red. 

CRYSTALLIZATION.  —  Hexagonal,  scalenohedral  class,  p.  42. 
Axis  c  =.  1.365. 

The  most  common  forms  on  the  Elba  crystals  are  the  unit 
rhombohedron  p  and  the  scalenohedron  n  =  (20.  :  20.  :  a  :  |*r)  ; 
{2243}.  The  rhombohedron  g  =  (a  :  oo  a  :  a  :  ^c  ;  { 1014}  also 


FIG.  334. 


FIG.  335. 


FIG.  336. 


occurs.     Thin  plate-like  crystals  are  the  rule  at  other  localities. 
Sometimes  grouped  in  rosettes,  as  in  the  "  Eisenrosen,"  Fig.  337. 


Supplement  angles.  — pp  =  94°  ;  nn  =  5 1  °  59' ;  cp  =  57' 


Fig-  337- 

37'; 


^•=37°  2' 


61°   13'. 


FIG.  337. 


FIG.  338. 


Eisenrosen,  Fibia  Switz. 


Radiated  reniform,  Geikie. 


Physical  Characters.     H.,  5.5  to  6.5.     Sp.  gr.,  4.9  to  5.3. 
LUSTRE,  metallic  to  dull.  OPAQUE. 

STREAK,  brownish  red  to  cherry  red.  TENACITY,  brittle  un- 

COLOR,  iron  black,  blackish  red  to  cherry  red.  less  micaceous. 

Sometimes  slightly  magnetic. 


THE  IRON  MINERALS.  2ig 

BEFORE  BLOWPIPE,  ETC. — Infusible.     Becomes  magnetic  in  re- 
ducing flame.     Soluble  in  hot  hydrochloric  acid.     In  borax  reacts 
for  iron. 
VARIETIES. 

Specular  Iron. — Brilliant  micaceous  or  in  crystals.  Black  in 
color. 

Red  Hematite. — Submetallic  to  dull,  massive,  blackish  red  to 
brownish  red  in  color. 

Red  Ochre. — Earthy  impure  hematite  usually  with  clay.  Often 
pulverulent. 

Clay  Ironstone. — Hard  compact  red  material  mixed  with  much 
clay  or  sand. 

Martite. — Octahedral  crystals,  probably  pseudomorphs. 

SIMILAR  SPECIES. — Resembles  at  times  the  other  iron-ores  and 
massive  cuprite.  It  is  distinguished  by  its  streak  and  strong  mag- 
netism after  heating  in  reducing  flame. 

REMARKS. — Usually  in  metamorphic  rocks,  probably  formed  from  bog  iron-ore  by 
pressure  and  heat.  Also  found  in  igneous  rocks.  Changes  by  action  of  atmosphere, 
water,  organic  matter,  etc.,  into  limonite,  siderite  and  magnetite.  About  72  per  cent, 
of  the  iron-ore  mined  in  the  United  States  is  hematite.  By  far  the  larger  part  is  obtained 
from  the  Marquette  and  Gogebic  ranges  of  Michigan  and  from  the  Mesabi  range  in 
Minnesota.  Smaller  but  by  no  means  inconsiderable  amounts  are  mined  in  New  York, 
Alabama,  Missouri  and  other  states. 

USES.  —  In  this  country  it  supplies  seven  eighths  of  all  the  iron 
ore  mined.  The  earthy  varieties  are  used  for  a  cheap  paint,  and 
some  massive  varieties  are  ground  for  paint  or  polishing  material. 

ILMENITE.  —  Menaccanite,  Titanic  Iron-Ore. 
COMPOSITION.  —  (Fe.Ti)2O3,  sometimes  containing  small  amounts 

of  Mg  or  Mn. 

FIG.  339.  FIG.  340. 


GENERAL  DESCRIPTION. — An  iron-black  mineral,  usually  mas- 
sive or  in  thin  plates  or  imbedded  grains  or  as  sand.  Also,  in 
crystals  closely  like  those  of  hematite  in  angle. 

CRYSTALLIZATION.  —  Hexagonal.     Class  of  third  order   rhom- 


220  DESCRIPTIVE   MINERALOGY. 

bohedron,  p.  48.      Axis  c  =  1.385.      Usually  thick  plates  showing 

basal  pinacoid^,  unit  prism  ;/zand  unit  rhombohedron  />,  Fig.  340,  or 

without   the  prism,  Fig.  339.      Supplement  angles  pp  =  94°  29'  ; 

tf-57°58'. 

Physical  Characters. — H,,  5  to  6.    Sp.  gr.,  4.5  to  5. 

LUSTRE,  submetallic.  OPAQUE. 

STREAK,  black  to  brownish-red.  TENACITY,  brittle. 

COLOR,  iron-black,  Slightly  magnetic. 

BEFORE  BLOWPIPE,  ETC. — Infusible  in  oxidizing  flame;  slightly 
fusible  in  reducing  flame.  In  salt  of  phosphorus  gives  a  red  bead 
which,  on  treatment  in  reducing  flame  becomes  violet,  slowly 
soluble  in  hydrochloric  acid  and  the  solution  boiled  with  tin  is 
violet  and  on  evaporation  becomes  rose-red. 

SIMILAR  SPECIES. — Differs  from  magnetite  and  hematite  in  the 
titanium  reactions. 

REMARKS.  — Menaccanite  occurs  in  crystalline  rocks,  often  with  magnetite.  It  is 
sometimes  altered  to  limonite  and  to  titanite. 

Immense  beds  occur  at  Bay  St.  Paul,  Quebec,  and  other  points  in  Canada.  Found 
also  in  the  county  of  Orange,  N.  Y.,  in  Massachusetts,  Connecticut,  and  elsewhere.  A 
Norwegian  locality  Kragero,  is,  for  its  large  crystals,  perhaps  the  most  celebrated. 

USES.  —  It  is  used  as  a  constituent  of  the  lining  of  puddling 
furnaces. 

GOETHITE. 

COMPOSITION. — FeO(OH).     Fe,  62.9  per  cent. 

GENERAL  DESCRIPTION. — A  yellow,  red  or  brown  mineral,  occurring  in  small,  dis- 
tinct, prismatic  crystals  (orthorhombic),  often  flattened  like  scales,  or  needle-like,  or 
grouped  in  parallel  position.  These  shade  into  feather-like  and  velvety  crusts.  Oc- 
curs also  massive  like  yellow  ochre. 

PHYSICAL  CHARACTERS. — Opaque  to  translucent.  Lustre,  adamantine  to  dull. 
Color,  yellow,  reddish,  dark-brown  and  nearly  black.  Streak,  yellow  or  brownish-yel- 
low. H.,  5  to  5.5.  Sp.  gr.,  4  to  4.4. 

BEFORE  BLOWPIPE,  ETC.— Fuses  in  thin  splinters  to  a  black  magnetic  slag.  In 
closed  tube  yields  water.  Frequently  reacts  for  manganese.  Soluble  in  hydrochloric 
acid. 

USES. — Goethite  is  an  ore  of  iron,  but  is  commercially  classed  with  limonite  under 
the  name  of  brown  hematite.  Large  deposits  are  reported  in  Minnesota. 

TURGITE.  —  Hydrohematite. 

COMPOSITION.  —  Fe4O5(OH)2,  Fe  =  66.2  per  cent. 

GENERAL  DESCRIPTION.  — Nearly  black,  botryoidal  masses  and  crusts  resembling 
limonite  but  with  a  red  streak  and  often  with  a  fibrous  and  satin-like  appearance  on 
fracture.  Also  bright  red  earthy  masses.  Usually  associated  with  limonite  or  hematite. 


THE   IRON  MINERALS.  221 

PHYSICAL  CHARACTERS.  —  Opaque.  Lustre,  submetallic  to  dull.  Color,  dark  red- 
dish-black in  compact  form,  to  bright  red  in  ocherous  variety.  Streak,  brownish  red. 
H.,  5.5-6.  Sp.  Or.,  4.29-4.68. 

BEFORE  BLOWPIPE,  ETC.  —  Decrepitates  violently,  turns  black  and  becomes  mag- 
netic. Yields  water  in  closed  tube  with  violent  decrepitation. 

SIMILAR  SPECIES.  —  Is  distinguished  from  limonite  and  hematite  by  its  violent  de- 
crepitation when  heated,  its  red  streak,  and  its  water  test. 

REMARKS. — Like  goethite  it  is  frequently  mistaken  for  and  classed  with  limonite. 
It  occurs  with  limonite  at  Salisbury,  Conn.,  and  in  various  localities  in  Prussia  and 
Siberia. 

USES.  —  It  is  an  ore  of  iron  but  commercially  is  classed  with  limonite. 

LIMONITE. — Bog-Ore,  Brown  Hematite. 

COMPOSITION.  —  Fe2(OH)6Fe2O3,    (Fe,    59.8    per  cent).      Fre- 
quently quite  impure,  from  sand,  clay,  manganese,  phosphorus,  etc. 
GENERAL  DESCRIPTION.  —  Never  crystallized,  but  grading  from 


FIG.  341. 


Stalactite  of  Limonite,  Hungary.     Columbia  University. 

the  loose,  porous  bog-ore  and  earthy  ochre  of  brown  to  yellow 
color  and  dull  lustre ;  to  compact  varieties,  often  with  smooth, 
black,  varnish-like  surface,  but  on  fracture  frequently  showing  a 
somewhat  silky  lustre  and  a  fibrous  radiated  structure.  Sometimes 
stalactitic,  Fig.  341,  and  often  with  smooth  rounded  surfaces  and 
in  pseudomorphs. 

Limonite  is  recognized  principally  by  its  yellowish -brown  streak 
and  absence  of  crystallization.  It  is  frequently  found  pseudomorph- 
ous,  the  original  iron-bearing  mineral  having  "  changed  "  to  limonite. 


222  .  DESCRIPTIVE  MINERALOGY. 

Physical  Characters.     H.,  5  to  5.5.     Sp.  gr.,  3.6  to  4. 

LUSTRE,  varnish-like,  silky,  dull.          OPAQUE. 

STREAK,  yellowish-brown,  TENACITY,  brittle,  earthy. 

COLOR,  brown,  nearly  black,  yellow  like  iron  rust 

BEFORE  BLOWPIPE,  ETC. — In  closed  tube  yields  water,  and  be- 
comes red.  Fuses  in  thin  splinters  to  a  dark  magnetic  slag.  Usu- 
ally reacts  for  silica  and  manganese.  Soluble  in  hydrochloric 
acid,  and  may  leave  a  gelatinous  residue. 

VARIETIES. 

Bog-Iron,  loosely  aggregated  ore  from  marshy  ground,  often 
intermixed  with  and  replacing  leaves,  twigs,  etc. 

Yellow  ochre,  umber,  etc.,  earthy  material,  intermixed  with  clay. 

Brown  clay  ironstone,  compact,  often  nodular  masses,  impure 
from  clay. 

SIMILAR  SPECIES. — Distinguished  from  other  iron-ores,  except 
goethite,  by  its  streak,  and  from  the  latter  by  lack  of  crystalliza- 
tion. 

REMARKS. — One  usual  result  of  the  decomposition  of  any  iron-bearing  mineral  is 
limonite.  The  decomposition  by  water,  carbon  dioxide  and  organic  acids,  produces 
soluble  iron  salts,  which  are  carried  to  some  valley  by  the  streams,  and  by  oxidation 
the  relatively  insoluble  limonite  forms  as  a  scum  on  the  water  and  then  sinks  to  the 
bottom  as  bog-ore.  In  time,  by  pressure,  heat,  etc.,  these  deposits  are  compacted. 

Limonite  constitutes  about  15  per  cent,  of  the  iron-ore  mined  in  the  United  Stales. 
The  largest  deposits  which  are  regularly  mined  exist  in  the  States  of  Virginia,  Alabama, 
Pennsylvania,  Michigan,  Tennessee,  and  Georgia. 

USES. — It  is  the  most  abundant  ore  of  iron,  but  is  relatively 
impure  and  low  in  iron.  The  earthy  varieties  are  used  as  cheap 
paints,  and  after  burning  are  darker  in  color,  and  are  called  burnt 
umber,  burnt  sienna,  etc. 

COPIAPITE.— Misy. 

COMPOSITION.— Fe2(FeOH)2(SO4)5  +  i8H2O,  (Fe2O3  30.6,  SO3 
38.3,  H2O  31.1  per  cent.)  often  with  some  A12O3  or  MgO. 

GENERAL    DESCRIPTION.  —  Brownish-yellow   to   sulphur- yellow 
mineral,    occurring   granular  massive,   or   in  loosely   compacted 
crystalline  scales,  rarely,  as  tabular  monoclinic  crystals.     It  has  a 
disagreeable  metallic  taste. 
Physical  Characters.     H.,  2.5.     Sp.  gr.,  2.1. 

LUSTRE,  pearly,  feeble,  TRANSLUCENT. 

STREAK,  yellowish-white,  TASTE,  metallic,  nauseous. 

COLOR,  brownish-yellow  to  sulphur-yellow. 


THE  IRON  MINERALS.  22 3 

BEFORE  BLOWPIPE,  ETC. — On  charcoal,  fuses  and  becomes  mag- 
netic. Yields  much  water  in  closed  tube,  and  some  sulphuric  acid. 
Soluble  in  water.  Decomposed  by  boiling  water.  With  soda  gives 
sulphur  reaction. 

REMARKS. — Copiapite  results  from  the  oxidation  of  pyrite,  raarcasite  and  pyrrho- 
j!1          tite.     It  occurs  with  these  minerals  and  with  other  sulphates. 



Melanterite,    FeSO4  +  7HzO.      A  pale   green,   fibrous   efflorescence  on   pyrite  or    - 
marcasife,  or  stalactitic  massive  or  pulverulent.     On  exposure  it  becomes  dull  yellowish 
ife.     Translucent.     Luster,  vitreous  or  dull.     Color,  vitriol  green  to  white.     Streak, 
hite.     H.,  2.     Sp.  gr.,  1.8  to  1.9.     Taste,  astringent,  sweetish. 

VIVIANITE.— Blue  Iron  Earth. 

COMPOSITION.— Fe3(PO4)2  -f-  8H2O.    (FeO  43.0,  P2O8  28.3,  H2O  28.7  per  cent.). 

GENERAL  DESCRIPTION. — Usually  found  as  a  blue  to  bluish  green  earthy  mineral, 
often  replacing  organic  material  as  in  bones,  shells,  horn,  tree  roots,  etc.  Also  found 
as  glassy  crystals  (monoclinic),  colorless  before  exposure,  but  gradually  becoming 
blue. 

PHYSICAL  CHARACTERS. — Transparent  to  opaque.  Lustre,  vitreous  to  dull.  Color 
and  streak,  colorless  before  exposure,  but  usually  blue  to  greenish.  H=l.5  to  2. 
Sp-  gr-,  =  2.58  to  2.69.  Brittle. 

BEFORE  BLOWPIPE,  ETC. — Fuses  easily  to  a  black  magnetic  mass  and  colors  flame 
pale  bluish-green,  especially  after  moistening  with  concentrated  sulphuric  acid.  In 
closed  tube  yields  water.  Soluble  in  hydrochloric  acid.  The  dried  powder  is  brown. 

SIDERITE.  —  Spathic  Ore. 

COMPOSITION.  —  FeCO3,  (FeO  62.1,  CO2  37.9  percent.)  usually 
with  some  Ca,  Mg  or  Mn. 

GENERAL   DESCRIPTION.  —  Occurs    in  FlG-  342- 

granular  masses  of  a  gray  or  brown  color 
and  also  in  masses  with  rhombohedral 
cleavage  and  in  curved  rhombohedral 
crystals,  Fig.  342.  'At  times  it  is  quite 
black  from  included  carbonaceous  matter. 

CRYSTALLIZATION. — Hexagonal.    Sca- 
lenohedral  class,  p.  42.   Axis  c  =  0.8 1 84. 

Usually  rhombohedrons  of  73°,  often  with  curved  (composite)  faces 
like  those  of  dolomite.     Optically, —  with  strong  double  refraction. 

Physical  Characters.     H.,  3.5  to  4.     Sp.  gr.,  3.83  to  3.88. 
LUSTRE,  vitreous  to  pearly.  OPAQUE  to  translucent. 

STREAK,  white  or  pale  yellow.  TENACITY,  brittle. 

COLOR,  gray,  yellow,  brown  or  black. 
CLEAVAGE,  rhombohedral  R/\R=  107°. 


224  DESCRIPTIVE  MINERALOGY. 

BEFORE  BLOWPIPE,  ETC. — Decrepitates,  become  black  and  mag- 
netic and  fuses  with  difficulty.  Soluble  in  warm  acids  with  effer- 
vescence. Slowly  soluble  in  cold  acids.  May  react  for  man- 
ganese. 

SIMILAR  SPECIES. — It  is  heavier  than  dolomite  and  becomes  mag- 
netic on  heating.  Some  stony  varieties  resemble  varieties  of  sphal- 
erite. 

REMARKS. — Siderite  occurs  as  beds  in  gneiss,  mica  and  clay-slate,  etc.,  and  as 
stony  impure  material  in  the  coal  formation.  Frequently  with  metallic  ores.  It  is 
probably  chiefly  formed  by  the  action  of  decaying  vegetation  on  limonite.  An  impure 
siderite  forms  the  chief  ore  in  Cornwall  and  other  English  mines.  It  is  found  at  Cats- 
kill,  N.  Y.,  and  in  the  coal  regions  of  Pennsylvania,  Ohio,  Virginia,  and  Tennessee, 
in  varying  quantities,  but  forms  only  a  little  over  one  per  cent,  of  American  iron  ore. 

USES. — It  is  used  as  an  ore  of  iron  and  when  high  in  manganese 
it  is  used  for  the  manufacture  of  spiegeleisen. 

CHROMITE.— Chromic  Iron. 

COMPOSITION. — FeCr2O4,  (FeO  32,  Cr2O3  68  per  cent.),  some- 
times with  A12O3  or  MgO  as  replacing  elements. 

GENERAL  DESCRIPTIOM. — Usually  a  massive  black  mineral  resem- 
bling magnetite.  Occurs  either  granular  or  compact  or  as  dissem- 
inated grains.  Rarely  in  small  octahedral  crystals.  Frequently 
with  more  or  less  serpentine,  mechanically  intermixed,  giving  rise 
to  green  and  yellow  spots  and  streaks. 

Physical  Characters.     H.,  5.5.     Sp.  gr.,  4.3  to  4.6. 
LUSTRE,  sub-metallic  to  metallic.  OPAQUE. 

STREAK,  dark-brown.  TENACITY,  brittle. 

COLOR,  black.  May  be  slightly  magnetic. 

BEFORE  BLOWPIPE,  ETC. — Infusible,  sometimes  slightly  fused  by 
reducing  flame,  and  then  becomes  magnetic.  In  salt  of  phos- 
phorus, in  oxidizing  flame,  gives  yellow  color  hot,  but  on  cooling 
becomes  a  fine  emerald-green.  With  soda  and  nitre  on  platinum 
fuses  to  a  mass,  which  is  chrome-yellow  when  cold.  Insoluble  in 
acids. 

SIMILAR  SPECIES. — Chromite  is  distinguished  from  other  black 
minerals  by  the  salt  of  phosphorus  reactions,  and  to  a  consider- 
able extent  by  the  serpentine  with  which  it  occurs. 

REMARKS. — Chromite  occurs  in  veins  and  masses  in  serpentine  and  has  been  found 
in  large  isolated  pockets  in  Southern  Pennsylvania  and  around  Baltimore,  Md.,  but 


THE   IRON  MINERALS. 


225 


the  richest  ore  has  been  exhausted,  and  most  of  the  ore  now  used  is  brought  from 
Turkey  and  from  New  Caledonia.  Extensive  deposits  are  also  found  in  Del  Norte,. 
San  Luis  Obispo,  Shasta  and  Placer  Counties,  California,  but  of  somewhat  lower 
grade. 

USES.  —  Chromite  is  the  source  of  the  various  chromium  com- 
pounds, such  as  potassium  bichromate,  used  in  calico  printing, 
electric  batteries,  etc.,  the  chrome  colors  and  pigments.  It  is  also 
used  in  the  manufacture  of  a  hard  chrome  steel  and  chrome  bricks 
of  a  highly  refractory  nature. 

COLUMBITE.— Tantalite. 

COMPOSITION.— Fe(CbO3)2,  (FeO  17.3,  Cb2O3  82.7),  but  grading  into  tantalite.  Fe 
(TaO3)2  without  change  of  crystalline  form.  Mn  is  often  present. 

GENERAL  DESCRIPTION. — Black,  often  iridescent  prismatic  crystals,  in  veins  of  gran- 
ite. More  rarely  massive. 

PHYSICAL  CHARACTERS. — Opaque.  Lustre,  bright  sub-metallic.  Color,  black. 
Streak,  dark-red  to  black.  H.,  6.  Sp.  Gr.,  5.4  to  6.5.  Brittle.  Cleavage  in  two 
directions  at  right  angles. 

BEFORE  BLOWPIPE,  ETC — Infusible.  Fused  with  potassium  hydroxide  and  boiled 
with  tin  gives  deep-blue  solution.  Insoluble  in  acids. 

USES.  —  It  is  the  chief  source  of  columbium  and  tantalium  salts. 

WOLFRAMITE. 

COMPOSITION.  —  (Fe.Mn)  WO4.     (About  76.5  per  cent.  WO3.) 

GENERAL    DESCRIPTION.  —  Heavy    dark -gray    to    black    sub- 
metallic    crystals,   orthorhombic    in    appearance,          FIG.  343. 
and  also  in  granular  or  columnar  masses. 

CRYSTALLIZATION. — Monoclinic.     Axes  a:  T>\ 
=  0.830  :  i  :  0.868,  /3  =  89°  22'. 

Usual  combination  shown  in  Fig.  343  of  unit 
prism  in,  ortho  pinacoid  a,  unit  clinodome  d  and 
-f  and  —  ortho  domes  c  =  (&  :  CQ&  :  y£c)  ;  { 102} 
angles,  mm  =  79°  23' ;  dd  =  81°  54' ;  as  =  61  ° 
54';  ^  =  62°  54'.  Zinnwald> 

Physical  Characters.  —  H.,  5  to  5.5.     Sp.  gr.,  7.  i  to  7.55. 

LUSTRE,  sub-metallic.  OPAQUE. 

STREAK,  dark-brown  to  black.  TENACITY,  brittle. 

COLOR,  dark-gray  to  black.  Slightly  magnetic. 

BEFORE  BLOWPIPE,  ETC.  —  Fuses  readily  to  a  crystalline  globule, 
which  is  magnetic.  In  salt  of  phosphorus  yields  a  reddish-yellow 
glass,  which  in  reducing  flame  becomes  green,  and  if  this  bead  is 
pulverized  and  dissolved  with  tin,  in  dilute  hydrochloric  acid,  a 
blue  solution  results. 
15 


226  DESCRIPTIVE  MINERALOGY. 

Partially  soluble  in  hydrochloric  acid,  the  solution  becoming 
blue  on  addition  of  tin. 

SIMILAR  SPECIES. — Distinguished  by  its  fusibility  and  specific 
gravity  from  similar  iron  and  manganese  minerals. 

REMARKS. — Wolframite  occurs  in  tin  veins  and  deposits  and  with  other  metallic 
minerals.  It  occurs  altered  to  Scheelite  and  also  pseudomorphous  after  scheelite.  It 
is  common  in  the  Cornwall  and  Zinnwald  tin  mines.  It  is  also  found  at  Flowe  Moun- 
tain, N.  C.,  Monroe  and  Trumbull,  Ct.,  Black  Hills,  Dakota,  Mine  la  Motte,  Mo.,  and 
elsewhere. 

USES.  —  It  is  used  to  make  an  alloy  of  tungsten  with  steel,  espe- 
cially valued  for  permanent  magnets  and  cutting  tools,  and  as  a 
source  of  tungsten  salts,  especially  tungstic  acid  and  sodium  tung- 
state,  which  are  used  in  dyeing,  and  as  material  to  render  cotton 
less  inflammable. 


CHAPTER   XXII. 
THE    MANGANESE    MINERALS. 

THE  minerals  described  are  :  * 

Sulphide  Alabandite  MnS 

Oxides  Braunite  Mn2O8  Tetragonal 

Ilaiismannite  MnsO4  " 

Pyrolusite  MnO2  Orthorhombic 

Psilomelane  MnO2  +  ( H2O.  K2O.  BaO) 

Wad  Mixture  of  oxides 

Hydroxide  Manganite  MnO(OH)  Orthorhombic 

Carbonate  Rhodochrosite  MnCO3  Hexagonal 

The  principal  economic  use  of  manganese  minerals  is  in  the  pro- 
duction of  the  alloys  with  iron,  speigeleisen  and  ferromanganese, 
used  in  the  manufacture  of  steel.  About  nine-tenths  of  all  the 
manganese  ore  mined  is  used  for  this  purpose.  The  method  of 
smelting  is  very  like  that  used  in  the  manufacture  of  pig-iron. 
Manganese  is  also  an  important  constituent  of  other  alloys,  espe- 
cially manganese  bronze  and  so-called  silver  bronze. 

Minor  uses  are  in  the  manufacture  of  chlorine,  bromine,  oxygen, 
disinfectants,  driers  for  varnishes  ;  as  a  decolorizer  to  remove  the 
iron  green  color  from  glass  and  also,  when  added  in  larger  quantity, 
to  give  an  amethystine  color  to  glass  and  pottery ;  in  the  ordinary 
dry  battery  ;  in  calico  printing,  making  green  and  violet  paints,  etc. 

Certain  iron  ores  are  very  rich  in  manganese  and  are  valuable  in 
making  spiegeleisen.  In  1902,*  901,214  long  tons  of  mangan- 
iferous  iron  ores  were  mined  in  the  United  States.  Also  a 
large  amount  of  franklinite  was  used  for  the  production  of  zinc 
oxide  and  65,246  tons  *  of  a  highly  manganiferous  by-product 
obtained. 

In  the  West,  especially  in  Colorado  and  Arizona,  manganese 
ores  often  carry  silver,  and  several  thousand  tons  are  smelted  each 
year  with  other  silver-bearing  minerals,  the  manganese  acting  as  a 
flux.  In  1902,  194,132  tons  were  thus  used. 

The   manganese    minerals    important   as    ores    are   the    oxides 

*The  common  silicate,  rhodonite,  which  has  no  economic  importance,  is  described 
under  the  silicates. 

227 


228 


DESCRIPTIVE  MINERALOGY. 


pyrolusite,  psilomelane  (including  wad),  braunite  and  manganite. 
In  1902  *  16,477  tons  were  produced  mainly  in  Montana,  Virginia 
and  Georgia,  while  235,576  tons  were  imported. 

ALABANDITE.  — Manganblende. 

COMPOSITION. — MnS,  (Mn  63.1,  S  36.9  per  cent.). 

GENERAL  DESCRIPTION.— A  dark  iron-black  metallic  mineral  with  an  olive  green 
streak.  Usually  massive,  with  easy  cubic  cleavage  and  occasionally  in  cubic  or  other 
isometric  crystals.  Also  massive  granular. 

PHYSICAL  CHARACTERS.— Opaque.  Lustre,  metallic.  Color,  deep  black  with  brown 
tarnish.  Streak,  olive  green.  H.,  3.5  to  4.  Sp.  gr.,  3.95  to  4.04.  Brittle. 

BEFORE  BLOWPIPE,  ETC. — Turns  brown,  evolves  sulphur  dioxide  and  fuses. 
Gives  sulphur  reactions  with  soda.  Soluble  in  dilute  hydrochloric  acid  with  rapid 
evolution  of  hydrogen  sulphide. 

SIMILAR  SPECIES It  is  distinguished  from  all  similar  species  by  its  streak. 

REMARKS.— The  other  manganese  minerals  are  derived  in  part  from  the  alteration 
of  this  species.  It  occurs  with  other  metallic  sulphides. 

BRAUNITE. 

COMPOSITION. — Mn2O3,  but  usually  containing  MnSiO3. 
GENERAL  DESCRIPTION. — Brownish  black  granular  masses  and 
occasional  minute  tetragonal  pyramids  almost  isometric,  t  =  0.985. 


Physical  Characters.     H.,  6  to  6.5. 
LUSTRE,  submetallic. 
STREAK,  brownish  black. 
COLOR,  brownish  black  to  steel  gray. 


Sp.  gr.,  4.75  to  4.82. 
OPAQUE. 
TENACITY,  brittle. 


BEFORE  BLOWPIPE,  ETC. — Infusible.  With  borax  an  amethys- 
tine bead.  Soluble  in  hydrochloric  acid,  evolving  chlorine  and 
generally  leaving  gelatinous  silica. 


FIG.  344. 


FIG.  345. 


FIG.  346. 


Braunite,  //=  77°  45'. 


Hausmannite,  //  =  74°  34' 


*  Mineral  Resources  of  the  United  States,  1902,  p.  138. 


THE  MANGANESE  MINERALS.  229 

SIMILAR  SPECIES. — Resembles  hausmannite,  but  has  a  darker 
streak  and  is  harder. 

USES. — It  occurs  in  large  quantities  in  India  and  smaller  amounts 
elsewhere,  and  is  an  ore  of  manganese. 

HAUSMANNITE. 

COMPOSITION. — MngO4.     (Mn,O8  69.0,  MnO  31.0  per  cent.). 

GENERAL  DESCRIPTION. — Black  granular  strongly  coherent  masses  occasionally  in 
simple  and  twinned  tetragonal  pyramids  which  are  more  acute  than  those  of  braunite, 

c=  I.I74- 

PHYSICAL  CHARACTERS.— Opaque.  Lustre,  submetallic.  Color,  brownish  black. 
Streak,  chestnut  brown.  H.,  5  to  5.5.  Sp.  gr.,  4.72  to  4.85.  Strongly  coherent. 

BEFORE  BLOWPIPE,  ETC. — Infusible.  Colors  borax  bead  amethystine.  Soluble 
in  hydrochloric  acid  with  evolution  of  chlorine. 

SIMILAR  SPECIES. — Differs  from  braunite  in  hardness,  streak  and  absence  of  silica. 

PYROLUSITE.— Black  Oxide  of  Manganese. 

COMPOSITION. — MnO2,    (Mn  63.2  per  cent.). 

GENERAL  DESCRIPTION. — A  soft  black  mineral  of  metallic  lustre. 
Frequently  composed  of  short  indistinct  crystals  or  radiated  needles, 
but  also  found  compact,  massive,  stalactitic,  and  as  velvety  crusts. 
It  is  also  the  common  dendrites,  Fig.  274.  Usually  soils  the 
fingers.  Frequently  in  alternate  layers  with  psilomelane. 

Physical  Characters.    H.,  I  to  2.5.  Sp.  gr.,  4.7  to  4.86. 

LUSTRE,  metallic  or  dull.  OPAQUE. 

STREAK,  black.  TENACITY,  rather  brittle. 
COLOR,  black  to  steel  gray. 

BEFORE  BLOWPIPE,  ETC. — Infusible,  becomes  brown.  Usually 
yields  oxygen  and  a  little  water  in  closed  tube.  Colors  borax 
bead  amethystine.  Soluble  in  hydrochloric  acid  with  evolution  of 
chlorine. 

SIMILAR  SPECIES. — Distinguished  by  its  softness  and  black  streak 
from  other  manganese  minerals. 

REMARKS. — Pyrolusite  results  from  the  dehydration  of  manganite  and  the  altera- 
tion of  alabandite  and  rhodochrosite.  It  is  usually  with  psilomelane,  hematite,  limon- 
ite  or  manganite. 

By  far  the  larger  part  of  all  that  is  mined  in  this  country  is  obtained  from  Crimera, 
Va.,  Cartersville,  Ga.,  and  Batesville,  Ark.  Other  deposits  exist  in  California,  Ver- 
mont and  North  Carolina.  Large  amounts  are  annually  imported  from  Cuba.  The 
purest  material  for  use  in  glass  making  is  obtained  near  Sussex,  N.  B.,  and  from  the 
Tenny  Cape  district,  Nova  Scotia. 


230  DESCRIPTIVE   MIXERALOGY. 

USES. — Pyrolusite  is  used  in  the  manufacture  of  chlorine  and 
oxygen,  and  in  the  preparation  of  spiegeleisen.  Also  in  coloring 
and  decolorizing  glass  and  as  an  oxidizing  agent  in  varnishes, 
linseed  oil,  etc. 

MANGANITE. 

COMPOSITION— MnO(OH),  (Mn 62.4,0  27.3,  H2O  10.3  percent). 
GENERAL  DESCRIPTION. — Occurs  in  long   and   short  prismatic 

FIG.  347. 


Manganite,  Ilefeld,  Hartz.     N.  Y.  State  Museum. 

(orthorhombic)  crystals  often  grouped  in  bundles  with  fluted  or 
rounded  cross-section  and  undulating  terminal  surface,  rarely  mass- 
ive, granular  or  stalactitic. 

Physical  Characters,     H.,  4.     Sp.  gr.,  4.2  to  4.4. 
LUSTRE,  submetallic.  OPAQUE. 

STREAK,  reddish  brown  to  black.  TENACITY,  brittle. 

COLOR,  steel  gray  to  iron  black. 

BEFORE  BLOWPIPE,  ETC. — Like  pyrolusite,  but  yields  decidedteslt 
for  water  and  very  little  oxygen. 

REMARKS. — Frequently  formed  by  deposition  from  water.     By  alteration  it  forms 
other  manganese  minerals  such  as  pyrolusite. 


THE  MANGANESE  MINERALS.  231 

PSILOMELANE.— Black  Hematite. 

COMPOSITION.— Perhaps  MnO2+  (H2O,  K2O  or  BaO)  or  H4MnOs, 
with  replacement  by  Ba  or  K. 

GENERAL  DESCRIPTION. — A  smooth  black  massive  mineral  com- 
monly botryoidal,  stalactitic  or  in  layers  with  pyrolusite.  Never 
crystallized. 

Physical  Characters.     H.,  5  to  6.  Sp.  gr.,  3.7  to  4.7. 
LUSTRE,  submetallic  or  dull.  OPAQUE. 

STREAK,  brownish  black.  TENACITY,  brittle. 

COLOR,  iron  black  to  dark  gray. 

BEFORE  BLOWPIPE,  ETC. — Infusible.*  In  closed  tube  yields 
oxygen  and  usually  water.  Soluble  in  hydrochloric  acid,  with 
evolution  of  chlorine.  A  drop  of  sulphuric  acid  added  to  the  solu- 
tion will  usually  produce  a  white  precipitate  of  barium  sulphate. 

SIMILAR  SPECIES. — Distinguished  from  pyrolusite  by  its  hard- 
ness, and  from  limonite  by  its  streak. 

REMARKS. — Its  localities  are  the  same  as  for  pyrolusite,  and  the  two  minerals  are 
usually  mined  together. 

USES. — As  for  pyrolusite ;  the  products,  however,  are  less  pure. 

WAD.— Bog  Manganese. 

COMPOSITION. — Mixture  of  manganese  oxides,  with  often  oxides  of  metals  other  than 
manganese  such  as  cobalt,  copper  and  lead. 

GENERAL  DESCRIPTION. — Earthy  to  compact  indefinite  mixtures  of  different  metal- 
lic oxides,  in  which  those  of  manganese  predominate.  Dark  brown  or  black  in  color; 
often  soft  and  loose,  but  sometimes  hard  and  compact. 

PHYSICAL  CHARACTERS.— Opaque.  Lustre  dull.  Color  brown  to  black.  Streak 
brown.  H.,  }/2  to  6.  Sp.  gr.,  3  to  4.26.  Often  soils  the  fingers. 

BEFORE  BLOWPIPE,  ETC.— As  for  psilomelane,  but  often  with  strong  cobalt  or 
copper  reactions. 

USES. — Wad  is  used  as  a  paint  and  in  the  manufacture  of  chlorine. 

RHODOCHROSITE. 

COMPOSITION.  —  MnCO3,  (MnO  61.7,  CO2  38.3  per  cent.)  with 
partial  replacement  by  Ca,  Mg  or  Fe. 

GENERAL  DESCRIPTION. — Rose  pink  to  brownish  red  rhombo- 
hedral  crystals,  usually  small  and  curved  like  dolomite.  Fre- 
quently massive  cleavable,  or  granular  or  compact.  Less  fre- 
quently botryoidal  or  incrusting. 

*  May  become  magnetic  from  impurities. 


232  DESCRIPTIVE  MINERALOGY. 

CRYSTALLIZATION.  —  Hexagonal.    Scalen-  FlG  ^ 

ohedral  class,  p.  42.  Axis  ^=.8184.  An- 
gles as  in  siderite.  Usual  form  a  rhombo- 
hedron  of  73°.  Optically  — . 


Physical  Characters.     H.,  3.51:04.5.     Sp. 
gr.,  3.3  to  3.6. 

LUSTRE,  vitreous  to  pearly.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  light  pink,  rose  red,  brownish  red  and  brown. 

CLEAVAGE,  parallel  to  rhombohedron. 

BEFORE  BLOWPIPE,  ETC.  —  Infusible,  but  decrepitates  violently 
and  becomes  dark  colored.*  In  borax  yields  amethystine  bead. 
Soluble  in  warm  hydrochloric  acid,  with  effervescence,  slowly  sol- 
uble in  the  cold  acid. 

SIMILAR  SPECIES.  —  Distinguished  from  rhodonite  by  form, 
cleavage,  effervescence  and  infusibility. 

REMARKS.  —  Principally  found  in  ore-veins,  especially  with  ores  of  manganese  and 
silver.  On  exposure,  sometimes  loses  color  or  becomes  spotted  by  oxide.  Found  at 
Mine  Hill,  N.  J.,  Butte,  Montana,  Austin,  Nev.,  and  elsewhere.  It  is  not  mined, 
however,  in  this  country.  The  only  producing  localities  are  Merionethshire,  Wales, 
and  Chevron,  Belgium. 

*  May  become  magnetic  from  impurities. 


CHAPTER   XXIII. 

NICKEL   AND    COBALT    MINERALS. 
THE    COBALT    MINERALS. 

THE  cobalt  minerals  described  are  : 

Sulphide  Linnaeite  (Co.Ni)3S4  Isometric 

Sulpharsenide  Cobaltite  CoAsS  Isometric 

Arsenide  Smaltite  (Co.Ni)As2  Isometric 

Arsenate  Erythrite  Coj(AsO<)r8H2O  Monoclinic 

The  metal  cobalt  has,  as  yet,  no  important  use ;  the  oxide  is 
used  to  impart  a  blue  color  to  glass  and  pottery.  The  chief  com- 
mercial compound  is  SMALT,  a  cobalt  glass,  the  cobalt  replacing 
the  calcium  of  ordinary  glass.  This  is  ground  and  used  as  a  fine 
blue  pigment,  which  is  unaltered  by  exposure. 

Cobalt  blue  and  Rinmann's  green  are  compounds  of  cobalt  with 
alumina  and  zinc  oxide  respectively. 

The  extraction  of  cobalt  from  a  nickeliferous  matte  is  an  elabor- 
ate chemical  operation  involving  solution  in  hydrochloric  acid,  pre- 
cipitation of  manganese  and  iron  as  basic  carbonates,  and  of  other 
metals  as  sulphides,  leaving  a  solution  of  chloride  of  nickel  and 
cobalt.  From  these  the  cobalt  is  precipitated  with  great  care,  by 
means  of  calcium  hypochlorite,  as  cobaltic  hydroxide,  after  which 
the  nickel  is  precipitated  as  hydroxide  by  lime-water.  By  using 
selected  ores,  mattes  especially  rich  in  cobalt  may  be  obtained  and 
for  ordinary  purposes  the  small  nickel  contents  are  neglected. 

About  200  tons  are  annually  produced. 

LINNAEITE.  —Cobalt  Pyrites. 

COMPOSITION.  — (Co.Ni).{S(,  often  with  some  Fe  or  Cu  replacing. 

GENERAL  DESCRIPTION.  —  A  steel-gray  metallic  mineral  usually 
in  granular  or  compact  masses  intermixed  frequently  with  chal- 
copyrite  ;  also  in  small  isometric  crystals,  usually  the  octahedron 
P>  Fig-  349,  or  this  with  the  cube  a,  Fig.  350. 


*  Cobalt  is  sometimes  found  in  arsenopyrite.     Asbolite  is  a  black  earthy  oxide  of 
cobalt  and  manganese. 

233 


234 


DESCRIPTIVE  MINER ALOG Y. 
FIG.  349.  FIG.  350. 


Physical  Characters.     H.,  5.5.     Sp.  gr.,  4.8  to  5. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  nearly  black.  TENACITY,  brittle. 

COLOR,  steel-gray,  with  reddish-tarnish. 
CLEAVAGE,  cubic  imperfect. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  fuses  to  a  magnetic  glob- 
ule, and  gives  off  fumes  of  sulphur  dioxide.  In  borax  bead  gives  a 
deep  blue  color,  and  with  frequent  replacement  of  borax  the  red 
bead  of  nickel  may  be  obtained.  Soluble  in  nitric  acid  to  a  red 
solution  and  with  separation  of  sulphur. 

REMARKS. — Occurs  with  other  cobalt  and  nickel  minerals  and  with  chalcopyrite, 
pyrrhotite,  bornite,  at  Mine  La  Motte,  Mo.,  Lovelock's  Station,  Nev.,  and  in  a  few 
other  American  localities. 

USES. — Does  not  occur  in  large  amounts,  but  is  used  as  a  source 
of  both  cobalt  and  nickel. 

COBALTITE.— Cobalt  Glance. 

COMPOSITION. — CoAsS,     (Co  35.5,  As  45.2,  S  19.3  per  cent.) 
GENERAL  DESCRIPTION. — A  silver  white  to  gray  metallic  min- 
eral resembling  linnaeite  in  massive  state  but  in  crystals  differing  in 
that  the  forms  are  the  pyritohedron  e,  and  cube  a,  and  these  com- 
bined, Fig.  353. 


FIG.  351. 


FIG.  352. 


FIG.  353. 


NICKEL   AND    COBALT  MINERALS:  235 

Physical  Characters.     H.,  5.5.     Sp.  gr.,  6  to  6.1. 

LUSTRE,  metallic.  OPAQUE. 

STREAK,  black.  TENACITY,  brittle. 

COLOR,  silver  white  to  gray.  CLEAVAGE,  cubic. 

BEFORE  BLOWPIPE,  ETC.  —  On  charcoal  fuses  to  a  magnetic 
globule  and  evolves  white  fumes  with  garlic  odor.  Unaltered  in 
closed  tube.  Soluble  in  warm  nitric  acid  to  rose-red  solution,  with 
residue  of  sulphur  and  arsenous  oxide. 

USES.  —  It  is  used  in  the  manufacture  of  smalt  and  in  porcelain 

painting. 

SMALTITE. 

COMPOSITION.  —  (Co.Ni)As2,  varying  widely  in  proportion  of 
cobalt  and  nickel,  and  usually  containing  some  iron  also. 

GENERAL  DESCRIPTION. — A  tin-white  to  steel-gray  metallic  min- 
eral resembling  linnaeite  and  cobaltite.     Usually  occurs  granular 
massive,  but  also  in  isometric  crystals,  especially  modified  cubes 
with  curved  faces. 
Physical  Characters.     H.,  5.5  to  6.     Sp.  gr.,  6.4  to  6.6. 

LUSTRE,  metallic.  OPAQUE. 

STREAK,  black.  TENACITY,  brittle. 

COLOR,  tin-white  to  steel-gray.  CLEAVAGE,  octahedral. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  fuses,  yields  white  fumes 
with  garlic  odor  and  leaves  a  magnetic  residue,  which,  when  oxi- 
dized in  contact  with  frequently  replaced  borax,  yields  successively 
slags  colored  by  iron,  cobalt,  nickel  and  possibly  by  copper.  In 
closed  tube  yields  arsenical  mirror.  Soluble  in  nitric  acid  to  a  red 
to  green  solution  according  to  proportion  of  cobalt  and  nickel. 
Partially  soluble  in  hydrochloric  acid,  especially  so  after  fusion, 
but  yields  no  voluminous  precipitate  of  yellow  arsenic  sulphide, 
as  does  arsenopyrite  when  similarly  treated. 

SIMILAR  SPECIES. — Differs  from  linnaeite  and  cobaltite  in  cleav- 
age, specific  gravity  and  blowpipe  reactions.  Differs  from  most 
arsenopyrite  and  tetrahedrite  in  the  cobalt  blue  slags  which  it 
yields.  It  can  best  be  distinguished  from  cobaltiferous  arseno- 
pyrite by  the  reaction  in  acids  after  fusion. 

REMARKS. — By  oxidation  produces  arsenates  of  cobalt  (erythrite)  and  nickel  (an- 
nabergite).  Occurs  in  veins  with  other  metallic  minerals,  especially  ores  of  copper, 
silver,  nickel  and  cobalt.  Especially  abundant  in  the  nickel  mines  of  Saxony.  Found 
at  Chatham,  Ct.,  Franklin  Furnace,  N.  J.,  and  in  California. 


236  DESCRIPTIVE  MINERALOGY. 

USES.  —  It  is  the  chief  ore  of  cobalt. 


Chloanthite,  NiAs2.  —  A  tin,  white  to  steel-gray  metallic  mineral  which  resembles 
smaltite,  and  by  replacement  of  nickel  by  cobalt  gradually  grades  into  that  mineral. 

ERYTHRITE. 

COMPOSITION.— Co3(AsO4)2.8H2O,     (CoO  37.5,  As,O5  38.4,  H2O  24.1  per  cent.). 

GENERAL  DESCRIPTION. — Groups  of  minute  peach  red  or  crimson  crystals  forming 
a  drusy  or  velvety  surface.  Also  in  small  globular  forms  or  radiated  or  as  an  earthy 
incrustation  of  pink  color. 

PHYSICAL  CHARACTERS.  —  Translucent.  Lustre,  adamantine  or  pearly.  Color, 
crimson,  peach  red,  pink  and  pearl  gray.  Streak,  paler  than  color.  H.,  1.5  to  2.5. 
Sp.  gr.,  2.91  to  2.95.  Flexible  in  laminae. 

BEFORE  BLOWPIPE,  ETC.  —  On  charcoal  fuses  easily,  evolves  white  fumes  with  garlic 
odor,  and  leaves  a  magnetic  residue,  which  imparts  .the  characteristic  blue  to  borax 
bead.  Soluble  in  hydrochloric  acid  to  a  light  red  solution. 

THE    NICKEL    MINERALS. 

The  nickel  minerals  described  are  : 

Sulphides  Millerite  NiS  Hexagonal 

Pentlandite  (Fe.Ni)S  Isometric 

Arsenide  Niccolite  NiAs  Hexagonal 

Arsenate  Annabergite  Nig(  AsO4)2-8H2O         Monoclinic 

Silicate  Garnierite  H3(Ni.Mg)SiO4  H2O 

Metallic  nickel  is  extensively  used  in  different  alloys,  and,  in- 
deed, was  first  obtained  as  a  residual  alloy  with  copper,  iron  and 
arsenic,  in  the  manufacture  of  smalt.  This  alloy  was  called  Ger- 
man silver  or  nickel  silver  and  largely  used  in  plated  silverware. 
Later,  a  large  use  for  nickel  was  found  in  coins,  the  United  States 
Mint  alone  using  nearly  one  million  pounds  between  1857  and 
1884.  In  this  alloy  copper  is  in  large  proportion,  the  present 
five  cent  piece  being  25  per  cent,  nickel,  75  per  cent,  copper,  and 
in  other  coins  the  percentage  of  copper  being  still  greater.  The 
most  extensive  application  of  nickel  at  present  is  in  the  manufac 
ture  of  nickel  steel  for  armor  plates  and  other  purposes.  The 
uses  of  nickel  steel  are  continually  increasing,  as  the  metal  has 
some  excellent  properties  possessed  by  no  other  alloy.  To  a 
limited  extent  nickel  is  used  in  a  nickel-copper  alloy  for  casing 
rifle  bullets.  An  alloy  of  iron  and  nickel  containing  30  per  cent, 
of  nickel  is  non-magnetic  and  is  used  in  electric  heaters  and  in  parts 
of  other  electrical  apparatus. 

A  sulphate  of  nickel  and  ammonium  is  also  manufactured  in 
large  amounts  for  use  in  nickel  plating. 


NICKEL   AND    COBALT  MINERALS.  237 

The  nickel  of  commerce  is  nearly  all  obtained  either  from  the 
garnierite  of  New  Caledonia  or  from  the  deposit  of  nickel-bearing 
sulphides  at  Sudbury,  Ontario.  The  garnierite  is  smelted  in  a 
low  blast  furnace,  with  coke  and  gypsum,  and  the  matte  of  nickel, 
iron  and  sulphur  thus  produced  is  alternately  roasted  and  fused 
with  sand,  in  a  reverberatory  furnace,  until  nearly  all  the  iron  has 
been  removed.  The  nickel  sulphide,  by  oxidation,  is  converted 
into  oxide. 

Nickel  oxide  is  obtained  from  the  pyrrhotite  and  chalcopyrite 
of  Sudbury,  Canada.  The  ore  is  first  roasted  to  remove  much 
of  the  sulphur,  and  is  then  smelted,  together  with  nickel -bear- 
ing slags  of  previous  operations.  A  nickel  matte  carrying  much 
copper  and  some  iron  is  produced  through  which  air  is  blown 
in  a  silica  lined  Bessemer  converter  and  most  of  the  iron  is 
carried  into  the  slag.  A  matte,  rich  in  nickel  and  copper,  results. 
This  may  be  directly  roasted  and  reduced  by  carbon  to  produce 
nickel-copper  alloys  for  the  manufacture  of  German  silver.  In 
order  to  separate  the  nickel  the  concentrated  matte  is  fused  with 
sodium  sulphate  and  coke,  after  which  the  melted  sulphides  are 
allowed  to  settle.  Under  these  conditions  the  copper  and  iron 
sulphides  form  a  very  fluid  mass  with  the  soda,  and,  with  some 
nickel,  rise  to  the  top  while  the  lower  portions  of  the  mass  are 
highly  nickeliferous.  The  two  layers  are  separated  and  each  is 
re-treated  in  much  the  same  manner.  The  nickel  sulphide  result- 
ing is  partially  roasted  and  is  fused  with  sand,  by  means  of  which 
most  of  the  iron  is  removed  as  a  silicate  in  the  slag.  The  nickel 
sulphide  remaining  is  by  oxidation  converted  into  the  oxide.  The 
oxide  is  sold  directly  to  steel  makers  or  may  be  reduced  to  metal 
by  mixing  with  charcoal  and  heating,  white  hot,  in  a  graphite 
crucible. 

The  world's  annual  output  of  nickel  is  about  10,000  short  tons. 
In  1903  the  U.  S.  produced*  11,200,000  pounds  almost  wholly 
from  foreign  ores. 

Nickel  is  now  successfully  refined  by  electrolysis,  but  the  de- 
tails of  the  process  are  jealously  guarded.  It  is  doubtful,  however, 
if  nickel  can  be  separated  from  cobalt  in  this  manner,  although 
most  other  impurities  are  removed. 

The  Mond  process  for  the  extraction  of  nickel  from  its  ore  and 

* Eng.  and  Min.  Jour.,  1904,  p.  4. 


238  DESCRIPTIVE  MINERALOGY. 

or  its  separation  from  cobalt  promises  to  become  important.  The 
process  is  based  on  the  discovery  that  when  carbon  monoxide 
is  passed  over  heated  nickel,  volatile  nickel  carbonyl,  Ni(CO)4, 
is  formed.  As  cobalt  does  not  react  in  this  way,  the  separation 
of  nickel  from  cobalt  is  easily  accomplished.  The  reconversion  of 
the  nickel  carbonyl  into  nickel  and  carbon  monoxide  is  a  simple 
operation. 

MILLERITE.  —  Capillary  Pyrites. 

COMPOSITION.  —  NiS,  (Ni  64.4  per  cent.). 

GENERAL  DESCRIPTION.  —  A  brass-colored  mineral  with  metallic 
lustre,  especially  characterized  by  its  occurrence  in  hair-like  or 
needle  crystals,  often  interwoven  or  in  crusts  made  up  of  radiating 
needles. 


Physical  Characters.     H.,  3  to  3.5.     Sp.  gr.,  5  3  to  5.65. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  greenish-black.  TENACITY,  crystals  elastic. 

COLOR,  brass  or  bronze  yellow. 

BEFORE  BLOWPIPE,  ETC.  —  On  charcoal  spirts  and  fuses  to  a 
brittle  magnetic  globule,  which  will  color  borax  red.  Soluble  in 
aqua  regia  to  a  green  solution,  from  which  potassium  hydroxide 
precipitates  a  green  nickelous  hydroxide  which  is  again  soluble  in 
ammonia  to  a  blue  solution. 

REMARKS.  —  Millerite  has  probably  been  formed  in  the  same  way  as  pyrite.  It  is 
probable  that  the  nickel  in  pyrrhotite  is  there  as  millerite.  Other  associates  are 
siderite,  hematite  and  dolomite.  In  the  United  States  it  has  been  obtained  chiefly 
from  the  Lancaster  Gap  mine,  in  Pennsylvania,  and  at  Antwerp,  N.  Y. 

USES.  —  It  is  a  valued  ore  of  nickel. 

PENTLANDITE. 

COMPOSITION.  —  (Fe.Ni)S. 

GENERAL  DESCRIPTION.  —  Light  bronze-yellow,  granular  masses 
of  metallic  lustre.  Often  showing  octahedral  cleavage  or  parting. 
Usually  with  chalcopyrite  or  pyrrhotite. 

Physical  Characters.     H.,  3.5-4.  Sp.  gr.,  4.6-5. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  black.  TENACITY,  brittle. 

COLOR,  light  bronze  yellow.  NOT  MAGNETIC. 


NICKEL   AND    COBALT  MINERALS.  239 

BEFORE  BLOWPIPE,  ETC.  —  Fuses  readily  to  a  magnetic  globule 
which  reacts  for  iron  and  nickel. 

USES.  —  Occurs  at  Sudbury,  Ontario,  with  pyrrhotite  and  chal- 
copyrite  and  is  mined  for  nickel  of  which  it  is  an  important  ore. 

NICCOLITE.— Copper  Nickel. 

COMPOSITION. — NiAs,  (Ni  43.9  per  cent.).  As  is  replaced  to 
some  extent  by  Sb  or  S,  and  Ni  by  Fe  or  Co. 

GENERAL  DESCRIPTION. — A  massive  mineral  of  metallic  lustre, 
characteristic  pale  copper  red  color  and  smooth  impalpable  struct- 
ure. Sometimes  the  copper-red  kernel  has  a  white  metallic  crust. 
Occasionally  occurs  in  small  indistinct  hexagonal  crystals. 

Physical  Characters.     H.,  5  to  5.5.     Sp.  gr.,  7.3  to  7.67. 

LUSTRE,  metallic.  OPAQUE. 

STREAK,  brownish-black.  TENACITY,  brittle. 

COLOR,  pale  copper  red  with  dark  tarnish. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  fuses  easily,  giving  off 
white  fumes  with  garlic  odor  and  leaving  a  magnetic  residue,  which 
will  color  borax  bead  red  and  sometimes  blue,  in  which  case 
the  borax  must  be  renewed  until  the  cobalt  is  all  removed.  In 
open  tube  yields  a  white  sublimate  and  a  yellowish- green  pul- 
verulent residue.  Soluble  in  concentrated  nitric  acid  to  a  green 
solution,  which  may  be  tested  as  under  millerite. 

SIMILAR  SPECIES. — Differs  from  copper  in  hardness,  black 
streak  and  brittleness. 

REMARKS. — Its  most  abundant  American  localities  are  at  Lovelock's,  Nevada,  and 
Tilt  Cove,  Newfoundland.  Also  obtained  at  Chatham,  Conn.,  and  Thunder  Bay, 
Lake  Superior. 

USES. — It  is  an  important  ore  of  nickel. 

ANNABERGITE.— Nickel  Bloom. 

COMPOSITION.— Ni3(AsO4)!1.8H2O,    (NiO  37.4  As2O5  38.5,  H2O  24.1  per  cen' 

GENERAL  DESCRIPTION. —  Pale  apple-green  crusts,  and  occasionally  very  small 
hair-like  crystals.  Usually  occurs  on  niccolite  or  smaltite. 

PHYSICAL  CHARACTERS. — Dull.  Color,  apple-green.  Streak,  greenish-white. 
H.,  i. 

BEFORE  BLOWPIPE,  ETC.— On  charcoal,  fuses  easily  to  a  magnetic  button,  and  be- 
comes dull  and  yellow  during  fusion,  evolving  garlic  odor.  In  closed  tube,  yields 
water  and  darkens.  With  borax,  gives  red  bead.  Soluble  in  nitric  acid. 

REMARKS. — Results  from  the  oxidation  of  niccolite  or  smaltite  in  moist  air. 


240  DESCRIPTIVE  MINERALOGY, 

GARNIERITE.— Noumeite. 

COMPOSITION.— H,(Ni.Mg)Si04  +  H2Oor2(Ni.Mg)5Si4O13.3H2O. 

GENERAL  DESCRIPTION. — Loosely  compacted  masses  of  brilliant 
dark-green  to  pale-green  mineral,  somewhat  unctuous.  Structure 
often  small  mammelonated,  with  dark-green,  varnish-like  surfaces, 
enclosing  dull  green  to  yellowish  ochreous  material.  Easily 
broken  and  earthy. 

Physical  Characters.     H.,  2  to  3.     Sp.  gr.,  2.27  to  2.8. 

LUSTRE,  varnish-like,  to  dull.  OPAQUE. 

STREAK,  light  green  to  white.  TENACITY,  friable. 

COLOR,  deep  green  to  pale  greenish-white. 

UNCTUOUS,  adheres  to  the  tongue. 

BEFORE  BLOWPIPE,  ETC.  —  Infusible,  decrepitates  and  becomes 
magnetic.  In  closed  tube  yields  water.  Borax  bead  gives  nickel 
reaction.  Partially  soluble  in  hydrochloric  and  nitric  acids. 

SIMILAR  SPECIES. — Differs  from  malachite  and  chrysocolla  in 
structure  and  unctuous  feeling.  Differs  from  serpentine  in  deep 
color  and  nickel  reaction. 

REMARKS.— Occurs  in  New  Caledonia  in  veins  in  serpentine,  with  chromite  and 
talc.  Possibly  derived  from  a  nickel-bearing  chrysolite.  Deposits  are  also  known  at 
Riddles,  Oregon  and  Webster,  N.  C. 

USES. — It  is  now  the  chief  source  of  nickel. 


CHAPTER   XXIV. 

ZINC    AND    CADMIUM    MINERALS. 
THE    ZINC    MINERALS. 

THE  zinc  minerals  described  are : 

Sulphide  Sphalerite  ZnS  Isometric 

Oxide  Zincite  ZnO  Hexagonal 

Sulphate  Goslarite,  ZnSO4.7H2O  Orthorhombic 

Carbonates  Smithsonite  ZnCO3  Hexagonal 

Hydrozindte  ZnCO8.2Zn(OH), 

Silicates  Willemite  Zn2SiOi  Hexagonal 

Calamine  ( ZnOH  )3SiO3  Orthorhombic 

The  important  ores  of  zinc  are  sphalerite,  smithsonite,  and  cala- 
mine ;  and,  in  New  Jersey,  willemite  and  zincite  occur  in  quantity 
sufficient  to  be  considered  ores.  A  large  amount  of  zinc  oxide 
is  also  made  from  franklinite  which  is  described  under  the  iron 
minerals. 

In  this  country,  Missouri,  Kansas,  Indiana  and  Illinois  yield 
most  of  the  zinc  ore,  although  other  important  regions  are  Penn- 
sylvania, New  Jersey  and  Virginia.  The  western  ore  contains 
lead  ore,  from  which  it  is  separated  by  concentration.  In  all,  in 
1903,  this  country  produced  156,318  tons  of  metallic  zinc  and 
59,810  tons  of  zinc  oxide  were  manufactured,*  besides  exporting 
37,619  tons  of  zinc  ore. 

The  principal  uses  of  metallic  zinc  are  in  galvanizing  iron  wire 
or  sheets  and  in  manufacturing  brass.  A  smaller  amount  is  made 
into  sheet  zinc  and  zinc  dust. 

Metallic  zinc  is  obtained  by  distillation  of  its  roasted  ores  with 
carbon.  The  sulphide  and  carbonate,  by  roasting,  are  converted 
into  oxide,  and  the  silicates  are  calcined  to  remove  moisture.  The 
impure  oxides,  or  the  silicate,  are  mixed  with  fine  coal  and  charged 
in  tubes  or  vessels  of  clay,  closed  at  one  end  and  connected  at  the 
other  end  with  a  condenser.  These  are  submitted  to  a  gradually 
increasing  temperature,  by  which  the  ore  is  reduced  to  metallic 

*  Engineering  and  Mining  Journal,  1904,  p.  4. 
16  241 


242 


DESCRIPTIVE  MINERAL  OG  Y. 


zinc,  and,  being  volatile,  distills,  and  is  condensed.  Apparently 
successful  processes  are  now  in  use  for  the  direct  deposition  of  zinc 
from  its  ores  by  electrolysis. 

Zinc  oxide,  ground  in  oil,  constitues  the  paint  zinc  white.  The 
oxide  may  be  made  from  the  metal  by  heating  it  to  a  temperature 
at  which  the  zinc  takes  fire  and  drawing  the  fumes  into  suitable 
condensers  ;  or,  as  in  this  country,  it  may  be  made  directly  from 
the  ore. 

SPHALERITE.  — Blende,  Zinc  Blende,  Black-jack. 

COMPOSITION.  —  ZnS  (Zn,  67  per  cent).  Often  contains  Cd, 
Mn,  Fe. 

GENERAL  DESCRIPTION.  —  A  mineral  of  resinous  lustre  shading 
in  color  from  yellow  through  brown  to  nearly  black  and  trans- 
parent to  translucent.  It  occurs  frequently  cleavable  massive  but 
also  in  crystals  and  in  compact  fine-grained  masses  or  alternate 
concentric  layers  with  galenite. 


FIG.  354. 


FIG.  355- 


FIG.  356. 


CRYSTALLIZATION.  —  Isometric.  Hextetrahedral  class,  p.  56. 
Usually  the  dodecahedron  d  with  the  tetrahedron  /  and  a  modify- 
ing tristetrahedron  o  =  (a  :  $a  :  3^) ;  {311}.  Fig.  355,  usually 
with  rounded  faces.  More  rarely  the  -|-  and  —  tetrahedron,  Fig. 
354,  and  sometimes  in  twin  crystals  like  Fig.  356. 

Index  of  refraction  for  yellow  light,  2.3692. 

Physical    Characters.     H.,  3.5  to  4.     Sp.  gr.,  3.9  to  4.1. 

LUSTRE,  resinous.  TRANSPARENT  to  translucent. 

STREAK,  white  to  pale  brown.       TENACITY,  brittle. 

COLOR,  yellow,  brown,  black  ;  rarely  red,  green  or  white. 

CLEAVAGE,  parallel  to  rhombic  dodecahedron  (angles  1 20°  and 
90°). 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  fuses  with  difficulty,  but 
readily  yields  a  sublimate,  sometimes  brown  at  first  from  cadmium 


\ 


ZINC  AND    CADMIUM  MINERALS.  243 

and  later  yellow  while  hot,  white  when  cold  and  becoming  bright 
green  if  moistened  and  ignited  with  cobalt  solution.  With  soda 
gives  a  sulphur  reaction.  Soluble  in  hydrochloric  acid  with  effer- 
vescence of  hydrogen  sulphide. 

SIMILAR  SPECIES. — Smaller  crystals  sometimes  slightly  resemble 
garnet  or  cassiterite,  but  are  not  so  hard. 

REMARKS. — Sphalerite  has  probably  been  formed  by  precipitation  from  water  by 
H2S  or  with  the  aid  of  decaying  organic  matter.  By  oxidation  it  changes  to  sulphate 
which  in  turn  may  be  decomposed  by  carbonates  and  silicates  forming  carbonates  and 
silicates  of  zinc.  Sphalerite  is  a  common  associate  of  lead  and  silver  ores  and  is  det- 
rimental, as  it  makes  their  treatment  more  difficult.  It  also  occurs  with  other  sulphides 
and  with  other  zinc  ores.  It  is  mined  in  southwest  Missouri,  at  Friedensville,  Pa.,  in 
the  southwestern  part  of  Wisconsin,  at  Pulaski,  Va.,  and  at  other  places.  In  small 
quantities  it  is  of  very  common  occurrence. 

USES. — It  is  an  important  ore  of  zinc  and  also  is  the  source  of 
most  of  the  cadmium  of  commerce. 

Goslarite. — ZnSO^.yHO,  is  formed  by  the  oxidation  of  sphalerite  in  damp  loca- 
tions. It  is  a  white  or  yellowish  earthy  mineral  with  nauseous  astringent  taste. 
Usually  an  incrustration  or  mass  shaped  like  the  original  sphalerite  or  in  stalactites. 
Rarely  needle-like  orthorhombic  crystals. 

ZINCITE.— Red  Zinc  Ore. 

COMPOSITION. — ZnO,  (Zn  80.3  per  cent.)  with  usually  some  Mn 
or  Fe. 

GENERAL  DESCRIPTION. — A  deep  red  to  brick-red  adamantine 
mineral  occurring  in  lamellar  or  granular  masses,  either  in  calcite 
or  interspersed  with  grains  and  crystals  of  black  franklinite  and 
yellow  to  green  willemite.  A  few  hexagonal  pyramids  have  been 
found. 
Physical  Characters.  H.(  4  to  4.5.  Sp.  gr.,  5.4  to  5.7. 

LUSTRE,  sub-adamantine.  TRANSLUCENT. 

STREAK,  orange  yellow.  TENACITY,  brittle. 

COLOR,  deep  red  to  orange  red. 

CLEAVAGE,  basal  and  prismatic  yielding  hexagonal  plates. 

BEFORE  BLOWPIPE,  ETC. — Infusible.  On  charcoal  gives  reactions 
for  zinc  as  described  under  sphalerite.  In  closed  tube  blackens,  but 
is  again  red  on  cooling.  With  borax  usually  gives  amethystine 
bead.  Soluble  in  hydrochloric  acid  without  effervescence. 

SIMILAR  SPECIES. — Differs  from  realgar  and  cinnabar  in  its  asso- 
ciates, infusibility  and  slow  volatilization. 


244  DESCRIPTIVE  MINERALOGY. 

REMARKS. — Occurs  in  quantity  only  in  Sussex  County,  N.  J.,  at  the  franklinite  lo- 
calities and  is  smelted  with  the  associated  franklinite,  willemite,  etc.,  and  the  zinc  re- 
covered. 

SMITHSONITE.  —  Dry  Bone,  Calamine. 

COMPOSITION.  —  ZnCO3  (ZnO,  64.8  ;  CO2,  35.2  per  cent). 
GENERAL  DESCRIPTION.  —  Essentially  a  white  vitreous  mineral 
but   often  colored  yellowish  or  brownish  by 
FlG-  357-  iron.      Structure  stalactitic  or   botryoidal,   or 

with  drusy  crystal  surface  ;  also  in  chalky 
cavernous  masses  and  granular.  Sometimes 
of  decided  colors,  as  deep  green  or  bright  yel- 
low, from  copper  or  cadmium  respectively. 

CRYSTALLIZATION. — Hexagonal.     Scaleno- 
hedral  class,  p.  42.    Axis  c=o.So6^.    Usually 
small  rhombohedrons  of  73°,  Fig.  357,  like  those  of  siderite. 
Optically  — . 

Physical  Characters.     H.,  5.     Sp.  gr.,  4.3  to  4.5. 

LUSTRE,  vitreous  to  dull.  TRANSLUCENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  shades  of  white,  more  rarely  yellow,  green,  blue,  etc. 
CLEAVAGE,  parallel  to  rhombohedron  (107°). 

BEFORE  BLOWPIPE,  ETC. — Infusible  but  readily  yields  white 
sublimate  on  coal,  often  preceded  by  brown  of  cadmium.  The 
sublimate  becomes  yellow  when  heated  and  becomes  bright  green 
when  moistened  with  cobalt  solution  and  then  heated.  Soluble 
in  acids  with  effervescence. 

SIMILAR  SPECIES. — Distinguished  from  calamine  by  its  efferves- 
cence and  from  other  carbonates  by  its  hardness. 

REMARKS. — Smithsonite  is  a  secondary  product  formed  usually  by  action  of  carbo- 
nated waters  on  other  zinc  ores  and  sometimes  by  atmospheric  action.  It  occurs  with 
the  other  ores  of  zinc,  especially  calamine,  and  with  ores  of  lead,  copper  and  iron.  In 
this  country  it  is  most  abundant  in  the  Missouri,  Virginia  and  Wisconsin  zinc  regions. 

USES. — Smithsonite,  being  easily  reduced  with  little  fuel,  is  a 
valuable  zinc  ore,  but  as  it  is  found  chiefly  near  the  surface,  the 
deposits  have  been  nearly  exhausted. 

HYDROZINCITE.— Zinc  Bloom. 

COMPOSITION.— ZnCO3'2Zn(OH)2,     (ZnO  75.3,  CO2  13.6,  H8O  n.i  per  cent.). 
GENERAL  DESCRIPTION. — Usually  a  soft  white  incrustation  upon  other  zinc  minerals, 
or  as  dazzling  white  stalactites,  or  earthy  and  chalk  like. 


ZINC  AND    CADMIUM  MINERALS.  245 

PHYSICAL  CHARACTERS.— Opaque.  Lustre,  dull  or  pearly.  Color,  pure  white  to 
yellowish.  Streak  shining  white.  H.,  2  to  2.5.  Sp.  gr.,  3.58  to  3.8. 

BEFORE  BLOWPIPE,  ETC.  —  Infusible.  Coats  the  coal  like  smithsonite.  Yields 
water  in  closed  tube.  Soluble  in  cold  dilute  acids  with  effervescence. 

WILLEMITE.  —  Troostite. 

COMPOSITION.  —  Zn2SiO4,  (ZnO,  72.9;  SiO2,  27.1);  often  with 
much  manganese  replacing  zinc. 

GENERAL  DESCRIPTION.  —  A  greenish  yellow  to  apple  green  or 
sulphur  yellow  mineral  when  pure,  but  often  FlG 

flesh  red  or  brownish  from  manganese  or 
iron.  Usually  occurs  granular,  but  also  as 
hexagonal  crystals  and  massive.  The  New 
Jersey  variety  is  known  by  its  associates, 
franklinite  and  zincite. 

CRYSTALLIZATION.  —  Hexagonal.  Class  of 
third  order  rhombohedron,  p.  48.  Axis  c  == 
0.6775.  Long  slender  prisms  of  yellowish 
color  and  coarse  thick  prisms  of  flesh  red  Franklin  Furnace,  N.  J. 
color  occur  at  Franklin  Furnace  ;  the  Altenberg  crystals  are  small 
and  brown  in  color. 

Physical  Characters.     H.,  5.5.     Sp.  gr.,  3.89  to  4.2. 

LUSTRE,  resinous.  TRANSPARENT  to  opaque. 

STREAK,  nearly  white.  TENACITY,  brittle. 

COLOR,  greenish  to  sulphur  yellow,  apple  green,  white,  flesh  red. 
CLEAVAGE,  basal  and  prismatic. 

BEFORE  BLOWPIPE,  ETC.  —  Fusible  in  thin  splinters  only  upon 
the  edges  to  a  white  enamel.  On  heating  with  cobalt  solution 
becomes  blue.  On  charcoal  with  soda  and  a  little  borax  yields 
the  zinc  coat.  Soluble  in  hydrochloric  acid  leaving  a  gelatinous 
residue.  Specimens  from  Franklin,  N.  J.,  phosphoresce  brilliantly 
under  the  influence  of  radium,  actinium,  ultra-violet  and  X-rays. 

SIMILAR  SPECIES. — Red  crystals  resemble  apatite  but  differ  in 
terminations,  rhombohedral  in  willemite  but  pyramidal  in  apatite. 
Willemite  is  also  heavier  than  apatite  and  gelatinizes. 

USES. — In  association  with  the  other  minerals  of  Franklin, 
N.  J.,  it  constitutes  a  valuable  ore  of  zinc.  This,  however,  is  its 
only  important  locality. 


246  DESCRIPTIVE  MINERALOGY. 

C ALAM I NE.— Electric  Calamine. 

COMPOSITION.— (ZnOH)2SiO3,  (ZnO,  67.5  ;  SiO2,  25.0;  H2O,  7.5 
per  cent.). 

GENERAL  DESCRIPTION.  —  A  white  or  brownish  white  vitreous 
mineral  frequently  with  a  drusy  surface  or  in  radiated  groups  of 
crystals,  the  free  ends  of  which  form  a  ridge  or  cocks- 
comb, Fig.  264,  and  more  rarely,  small  distinct  trans- 
parent crystals.  It  occurs  also  granular,  stalactitic, 
botryoidal  and  as  a  constituent  of  some  clays. 

CRYSTALLIZATION. —  Orthorhombic.  Hemimorphic 
class,  p.  35.  Axes  d  :  ~b  :  c  =  0.783  :  I  :  0.478.  The 
crystals  are  usually  tabular,  the  broad  face  being  the 
brachypinacoid  b,  while  the  prism  m  is  relatively 
small,  v  is  the  pyramid  2d  :  b  :  2c ;  {121}. 

Optically  +  ,  with  acute  bisectrix  vertical.      2E  for 
yellow  light  =  78°  39'. 

Physical  Characters.         H.,  4.5  to  5.     Sp.  gr.,  3.4  to  3.5. 
LUSTRE,  vitreous  to  pearly.  OPAQUE  to  transparent. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  yellow  to  brown,  white,  colorless,  rarely  blue  or  green. 
Cleavage,  prismatic. 

BEFORE  BLOWPIPE,  ETC. — Fusible  only  in  finest  splinters.  With 
soda  and  borax,  on  charcoal  yields  a  white  coating,  which  is  made 
bright  green  by  heating  with  cobalt  solution.  In  closed  tube, 
yields  water.  With  acids,  dissolves,  leaving  a  gelatinous  residue. 

SIMILAR  SPECIES. — It  is  softer  than  prehnite,  harder  than  cerus- 
site,  and  gelatinizes  with  acids.  It  differs  from  willemite  in  water 
reaction,  and  from  stilbite  in  difficulty  of  fusion. 

REMARKS. — Calamine  seems  to  be  formed  by  the  action  of  hot  silica  bearing  waters 
upon  other  zinc  ores,  especially  sphalerite.  It  is  often  disseminated  through  a  clay, 
from  which  it  is  gradually  segregated  and  crystallized.  Its  most  important  locality  in 
America  is  at  Granby,  Mo.  It  is  also  found  in  quantity  at  Sterling  Hill,  N.  J.,  and 
Bertha,  Va.  Abroad,  it  is  exported  from  Greece,  and  is  mined  in  large  amounts  in 
Silesia  and  the  Rhenish  Provinces  of  Germany. 

USES.  —  It  is  a  valuable  ore  of  zinc,  usually  free  from  volatile 
impurities. 

THE    CADMIUM    MINERALS. 

The  only  cadmium  mineral  is  the  sulpltide,  GREENOCKITE,  CdS. 
About  five  tons  per  year  of  cadmium  are  obtained  from  the  Si- 


ZINC  AND    CADMIUM  MINERALS.  247 

lesian  zinc  ores.  The  first  fumes  are  redistilled  and  finally  reduced 
with  carbon.  The  metal  is  used  in  fusible  alloys  and  certain  forms 
of  silver  plating.  The  sulphide  forms  a  splendid  yellow  pigment 
unaltered  by  exposure. 

GREENOCKITE. 

COMPOSITION.— CdS,     (Cd,  77.7  per  cent.) 

GENERAL  DESCRIPTION. — Usually  a  bright  yellow  powder  upon  sphalerite,  or  a 
yellow  coloration  in  smithsonite.  Very  rarely  as  small  hemimorphic  hexagonal  crys- 
tals, c  —  O.Sin. 

PHYSICAL  CHARACTERS. — Translucent.  Lustre  earthy  or  adamantine.  Color  yel- 
low to  orange  yellow  or  bronze  yellow.  Streak  orange  yellow.  H.,  3  to  3.5.  Sp. 
gr.,  4.9  to  5.0. 

BEFORE  BLOWPIPE,  ETC. — Infusible,  but  is  easily  volatilized  in  the  reducing  flame, 
coating  the  coal  with  a  characteristic  brown  coat  and  a  iridescent  tarnish.  In  closed 
tube,  turns  carmine  red  on  heating,  but  is  yellow  on  cooling.  Soluble  in  strong 
hydrochloric  acid,  with  effervescence  of  hydrogen  sulphide. 


CHAPTER   XXV. 

TIN,  TITANIUM,  AND   THORIUM   MINERALS. 
THE    TIN    MINERALS. 

THE  minerals  described  are  : 

Sulphide  Stannite  (Cu.Sn.Fe)S  Isometric 

Oxide  Cassiterite  SnO2  Tetragonal 

Tin  is  also  found  as  an  occasional  constituent  of  tantalite  and 
other  tantalates. 

Cassiterite  is  the  only  ore  of  tin,  and  while  it  occurs  or  has  been 
reported  from  nine  or  ten  states,  no  tin  is  now  produced  *  in  this 
country.  The  world's  supply  of  tin,  amounting  yearly  to  about 
90,000  long  tons,  comes  chiefly  from  the  East  India  Islands,  Tas- 
mania, Bolivia  and  Cornwall,  England. 

The  principal  use  of  tin  is  for  the  manufacture  of  tin  plate  — 
sheet-iron  coated  with  tin  —  which  is  used  for  making  cans,  house- 
hold utensils,  etc.  Tin  is  also  largely  used  in  alloys,  such  as  bronze, 
bell  metal,  pewter,  solder  and  tin  amalgam.  Tinfoil  is  also  made 
from  it. 

The  ore  as  mined  is  first  separated  from  gangue  and  impurities 
by  washing,  jigging,  etc.,  and  if  necessary,  is  then  calcined  or 
roasted,  to  remove  volatile  elements,  such  as  sulphur,  arsenic, 
antimony. 

The  concentrated  and  purified  ore  may  then  be  smelted  with 
carbon  in  a  shaft  furnace.  The  modern  practice  is,  however,  to 
smelt  the  ore  for  several  hours  in  a  reverberatory  furnace  with  coal. 
The  liquid  tin  is  drawn  off  and  the  slags  are  resmelted  at  a 
higher  temperature,  frequently  requiring  the  addition  of  iron  or  of 
lime  to  aid  in  the  separation  of  the  tin,  which  they  still  contain.  The 
impure  metal  obtained  is  slowly  heated  to  a  temperature  but  little 
above  the  melting  point  of  tin  ;  comparatively  pure  tin  separates 
and  this  is  further  purified  by  oxidation.  This  oxidation  is  accom- 
plished either  by  forcing  green  wood  under  the  liquid  metal  causing 

*The  Temescal  mines  of  California  produced  about  120  tons  from  1890  to  1892  but 
have  since  been  unproductive. 

248 


TIN,    TITANIUM,    AND    THORIUM  MINERALS. 


249 


violent  agitation  or  by  repeatedly  pouring  the  melted  tin  in  a  thin 
stream  from  ladles.     Tin  may  also  be  refined  by  electrolysis. 

STANNITE.— Tin  Pyrites. 

COMPOSITION. — (Cu.Sn.Fe)S.     Uncertain. 

GENERAL  DESCRIPTION. — A  massive,  granular  mineral,  of  metallic  lustre  and  steel- 
gray  color.  It  is  often  intermixed  with  the  yellow  chalcopyrite. 

PHYSICAL  CHARACTERS. — Opaque.  Lustre  metallic.  Color  steel  gray  to  nearly 
black.  Streak  black.  H=4.  Sp.  gr.,  4.5  to  4.52.  Brittle. 

BEFORE  BLOWPIPE,  ETC. — In  the  reducing  flame  fuses.  In  the  oxidizing  flame 
yields  SO2,  and  is  covered  by  white  oxide,  which  becomes  bluish  green  when  heated 
with  cobalt  solution.  Soluble  in  nitric  acid  to  a  green  solution,  with  separation  of 
sulphur  and  oxide  of  tin.  With  soda,  gives  sulphur  reaction. 

CASSITERITE. — Stream  Tin.     Tin  Stone. 

COMPOSITION. — SnO2,  (Sn  78.6  per  cent),  and  usually  with  some 
Fe2O3,  and  sometimes  Ta2O6,  As2O5,  SiO2  or  Mn2O3. 

GENERAL  DESCRIPTION. — A  hard  and  heavy  brown  to  black 
mineral  occurring  either  in  brilliant  adamantine  crystals  or  more 
frequently  in  dull  botryoidal  and  kidney-shaped  masses  and  rounded 
pebbles,  often  with  a  concentric  or  fibrous  radiated  structure. 

FIG.  360.  FIG.  361.  FIG.  362. 


Stoneham,  Me. 


Cornwall,  Eng. 


Zinnwald. 


CRYSTALLIZATION.  —  Tetragonal.  Axis  c  =  0.672.  Common 
forms  are  the  unit  first  and  second  order  pyramids  and  prisms  /,  a, 
m,  and  d,  and  the  ditetragonal  pyramid  z  =  (a  :  \a  :  T,C]  ;  (321). 
Supplement  angles  // =  58°  19'  ;  dd  =  46°  28'  ;  viz  =  24°  59'. 

Frequently  twinned  parallel  to  the  second  order  pyramid,  Fig. 
362. 

Optically  +  with  high  indices  of  refraction  1.996  and  2.093. 

Physical  Characters.     H.,  6  to  7.     Sp.  gr.,  6.8  to  7.1. 
LUSTRE,  adamantine  to  dull.         OPAQUE  to  translucent. 
STREAK,  white  or  pale  brown.       TENACITY,  brittle. 


250  DESCRIPTIVE  MINERALOGY. 

COLOR,  brown  to  nearly  black,  sometimes  red,  gray,  or  yellow. 
CLEAVAGES,  indistinct  pyramidal  and  prismatic. 

BEFORE  BLOWPIPE,  ETC.  —  Infusible,  but  in  powder  becomes  yel- 
low and  luminous.  With  cobalt  solution  the  powder  or  any  sub- 
limate is  made  bluish  green.  On  charcoal  with  soda  may  be  re- 
duced, yielding  metallic  button  and  a  faint  white  sublimate  close  to 
the  assay.  Insoluble  in  acids  and  almost  so  in  salt  of  phosphorus 
or  borax  in  which  it  usually  gives  some  manganese  or  iron  reaction. 

VARIETIES. 

Tin  Stone. — Crystals  and  granular  masses. 

Wood  Tin. — Masses  with  concentric  structure,  the  zones  being 
of  different  color  and  internally  fibrous. 

Stream  Tin. — Rounded  pebbles  and  grains  found  in  alluvial  de- 
posits. 

SIMILAR  SPECIES. — The  high  specific  gravity  distinguishes  it  from 
silicates  which  it  resembles,  and  the  infusibility  and  insolubility 
distinguish  it  from  wolframite,  etc. 

REMARKS. — Cassiterite  is  found  in  veins  in  granite,  gneiss,  mica,  schist  and  similar 
rocks  with  quartz,  wolframite  and  scheelite,  and  also  with  certain  sulphides  and  oxides. 
It  occurs  also  in  alluvial  deposits,  as  stream  tin.  It  is  practically  unchanged  by  atmos- 
pheric influences.  The  East  Indian  settlements  of  Malacca,  Banca  and  Bilitong  are 
the  greatest  producers  of  tin  ore.  They  are  closely  followed  by  the  mines  in  New 
South  Wales,  Queensland  and  Tasmania.  Tin  is  also  mined  in  large  quantities  at  the  an- 
cient localities  in  Cornwall,  England.  In  America  the  chief  localities  are  in  the  Harney 
Peak  region  in  South  Dakota;  near  Temescal,  California,  and  at  Durango,  Mexico. 
It  has  been  found  also  in  New  Hampshire,  Virginia,  Maine,  Massachusetts,  Alabama, 
Wyoming  and  Montana  but  has  not  yet  been  obtained  from  any  American  locality  in 
quantity  sufficient  to  be  called  important. 

USES. — All  tin  is  made  from  cassiterite.  The  artificial  oxide  is 
used  as  a  polishing  powder. 

THE    TITANIUM    MINERALS. 

The  minerals  described  are  : 

Oxides  Rutile  TiO2  Tetragonal 

Octahedrite  TiO2 

Brookite  TiO,  Orthorhombic 

Titanium  is  also  a  constituent  of  ilmenite  and  titanite,  elsewhere 
described,  and  occurs  in  some  other  minerals. 

Oxide  of  titanium  is  used  to  impart  an  ivory-like  appearance  to 


TIN,    TITANIUM,    AND    THORIUM  MINERALS. 


251 


porcelain,  but  otherwise  is  of  no  commercial  importance.     A  few 
hundred  pounds  only  are  marketed  each  year  in  the  United  States. 

The  metal  is  only  produced  as  a  chemical  curiosity  or  for  the 
study  of  its  properties.  It  is  prepared  by  the  reduction  of  its 
oxide  by  carbon  at  the  highest  available  temperature  of  the  electric 
furnace.  In  the  form  thus  obtained  it  carries  a  small  percentage 
of  carbon,  is  the  most  infusible  of  metals  and  almost  equals  the 
diamond  in  hardness. 

RUTILE.  —  Nigrine. 

COMPOSITION. — TiO2,   (Ti  61  per  cent.). 

GENERAL  DESCRIPTION. — Brownish  red  to  nearly  black  prismatic 
crystals  often  included  in  other  minerals  in  hair-like  or  needle- 
like  penetrations.  Also  coarse  crystals  embedded  in  quartz, 
feldspar,  etc.,  or  in  parallel  and  crossed  and  netted  needles  upon 
hematite  or  magnetite.  Occasionally  massive  when  black  and  iron 
bearing. 

FIG.  363.  FIG.  364.  FIG.  365. 


Magnet  Cove,  Ark. 

CRYSTALLIZATION. —  Tetragonal.  Axis  c  =  0.644.  Very  close 
to  cassiterite  in  angles  and  forms.  Usual  combinations  are  unit  first 
and  second  order  pyramids,  /  and  d,  and  first  and  second  order 
prisms,  m  and  a.  Often  twinned  in  knees,  Fig.  365,  and  rosettes, 
Fig-  364.  As  fine  hair-like  inclusions,  Fig.  258.  Prisms  often 
striated  vertically. 

Supplement  angles //==  56°  52'  ;  ^=45°  2'. 

Optically  +  with  very  high  indices  of  refraction  2.616  and  2.902 
for  yellow  light. 
Physical  Characters.     H.,  6  to  6.5,  Sp.  gr.,  4.15  to  4.25. 

LUSTRE,  adamantine  to  nearly  metallic.     OPAQUE  to  transparent. 

STREAK,  white,  pale  brown.  TENACITY,  brittle. 

COLOR,  reddish  brown,  red,  black,  deep  red  when  transparent. 

CLEAVAGES,  prismatic  and  pyramidal. 


252  DESCRIPTIVE  MINERALOGY. 

BEFORE  BLOWPIPE,  ETC.  —  Infusible.  In  salt  of  phosphorus 
dissolves  very  slowly  in  the  oxidizing  flame  to  a  yellow  bead 
which  becomes  violet  in  the  reducing  flame.  Insoluble  in  acids. 

SIMILAR  SPECIES.  —  It  is  redder  and  of  lower  specific  gravity 
than  cassiterite.  The  nearly  metallic  lustre,  weight  and  infusibility 
separate  it  from  garnet,  tourmaline,  vesuvianite,  and  pyroxene. 

REMARKS. — Widely  distributed  and  associated  with  many  minerals  in  which  it  is 
usually  embedded.  Little  altered  by  atmospheric  influences.  Found  in  many  Ameri- 
can localities;  prominent  among  them  are  Nelson  Co.,  Va.,  Graves  Mountain,  Ga., 
Warwick,  N.  Y.,  Warren,  Me.,  and  Magnet  Cove,  Ark. 

USES.  —  Rutile  is  used  to  color  porcelain  yellow  and  to  give  the 
desired  bluish  white  tint  to  artificial  teeth. 


Octahedrite. — TiO2.  In  small  pyramidal  tetragonal  crystals  2—1.777.  Either 
black  opaque  and  nearly  metallic,  or  brown  translucent  and  adamantine. 

Brookite  =-.  TiO2.      Orthorhombic.      Axes  a  :  b  :  f  =  0.842  :  I  :  0.944. 
Either  brown  translucent  crystals  which  are  thin  and  tabular,  or  black  opaque  crystals 
of  varied  habit. 

THE    THORIUM    MINERALS.* 

The  minerals  described  are  : 

Phosphate  Monazite  (Ce,  La,  Di)PO4,  Monoclinic 

Silicate  Thorite  ThSiO4,  Tetragonal 

The  oxide  of  thorium,  thoria,  has  become  very  important  of  late 
years  from  its  property  of  emitting  intense  white  light  when  held  in 
the  flame  of  a  Bunsen  gas  burner.  The  mantle  of  the  Welsbach  in- 
candescent gas  lamp  consists  of  about  99  per  cent,  of  thorium  oxide 
with  one  per  cent,  of  cerium  oxide.  The  price  of  thoria  has 
recently  been  greatly  reduced  owing  to  competition  and  improved 
methods  of  production  and  to  the  low  price  of  Brazilian  monazite. 

The  chief  source  of  thoria  is  the  phosphate  of  cerium  mineral, 
monazite.  This  mineral  carries  salts  of  thorium  as  impurities  and 
in  quantities  varying  from  traces  to  as  much  as  18.5  per  cent,  of 
thorium  oxide.  The  mineral  thorite  is  also  employed  in  the  pro- 
duction of  thoria,  but,  although  it  contains  over  20  per  cent,  of  the 
oxide,  it  is  much  more  difficult  to  obtain  in  quantity. 

Monazite  sand  occurs  in  Brazil   in   immense   deposits,   certain 

*  The  following  minerals  also  are  usually  rich  in  thoria  and  would  be  valuable  if  found 
in  quantity  :  Gummite  (0—42  per  cent.),  mackintoshite  (45-46  per  cent.),  aeschynite 
(15-17  per  cent.),  zirkelite  (7-8  percent.),  tscheffkinite  (0-21  per  cent),  yttrialite 
(12  per  cent),  caryocerite  (13-14  per  cent),  euxenite  (0-6  per  cent.),  pyrochlore 
( 8  per  cent. ) . 


TIN,    TITANIUM  AND    THORIUM  MINERALS.          253 


beaches  consisting  of  90  per  cent,  of  monazite.  The  production 
of  the  United  States  is  increasing  and  in  1902  was  802,000 
pounds,*  principally  from  North  Carolina. 

Thoria  is  manufactured  by  methods  which  are  carefully  guarded. 
It  is  stated  that  the  method  usually  employed  is  to  decompose  the 
monazite  sand  in  hot  sulphuric  acid  (i  :  i).  The  sulphates  dis- 
solved in  water  are  converted  into  oxalates  by  oxalic  acid  from 
which  the  thorium  oxalate  is  separated  by  means  of  a  large  excess 
of  ammonium  oxalate,  precipitated  by  hydrochloric  acid  and  after- 
wards transformed  into  thorium  nitrate  which  on  heating  yields  the 
oxide. 

/MONAZITE, 

COMPOSITION. — (Ce.La.Di)PO4,  but  with  notable  quantities  of 
thorium  and  silicon  and  frequently  small  amounts  of  erbium  and 
ytterbium,  o— &  ^^U^i^^^^  • 

GENERAL  DESCRIPTION.  —  Small,  brown,  resinous  crystals,  or 
yellow,  translucent  grains,  disseminated  or  as  sand.  Sometimes  in 
angular  masses. 

CRYSTALLIZATION.  —  Monoclinic.  Axes  a  :  b  :  c  =  0.969  :  i  : 
0.926;  ft  =  76°  20'.  Crystals  are  usually 
small  and  flat,  but  sometimes  large.  Fig. 
366  shows  the  pinacoids  a  and  b,  the  unit 
pyramid,  prism  and  dome  /,  m  and  o  and 
the  prism  /=  (20,  :  b  :  cor) ;  {120}.  Sup- 
plement angles  mm  =86°  34'  ;  ad  =  39° 

i2',//=73°  19'- 

OPTICALLY -f-,  with  axial  plane  nearly  # 
and  acute  bisectrix  nearly  vertical.  Axial 
angle  in  red  light  2.E  =  29°  to  31°. 

Physical  Characters.  —  H.,  5-5.5. 

LUSTRE,  resinous. 

STREAK,  white. 

COLOR,  clove  or  reddish  brown, 
yellow. 

BEFORE  BLOWPIPE,  ETC.  Turns  gray  when  heated,  but  does  not 
fuse.  Is  decomposed  by  hydrochloric  acid  with  a  white  residue. 
Solutions  added  to  a  nitric  acid  solution  of  ammonium  molybdate 
produce  a  yellow  precipitate. 


FIG.  366. 


Sp.  gr.,  4-9-5-3- 
OPAQUE,  to  translucent. 
TENACITY,  brittle. 
CLEAVAGE,  basal,  perfect. 


*  Mineral  Resources,  1902,  23. 


254  DESCRIPTIVE  MINERALOGY. 

REMARKS.  —  Monazite  is  found  in  considerable  quantities  in  North  and  South  Caro- 
ina,  as  sand  and  as  a  rock  constituent.  The  Brazilian  sand  which  is  now  the  chief 
source  of  supply  is  found  at  Bahia,  Minas  Geraes,  Caravellas,  San  Pedro  and  Antigua. 

USES.  —  It  is  the  chief  source  of  the  thoria  used  in  mantles  for 
incandescent  gas  lighting.  It  is  also  the  chief  source  of  the  rare 
elements  cerium,  lanthanum  and  didymium. 

THORITE.  —  Orangite. 

COMPOSITION.  —  ThSiO4,  carrying  some  water. 

GENERAL  DESCRIPTION.  —  Black  or  orange-yellow  tetragonal  crystals  like  those  of 
zircon.  Also  found  massive. 

PHYSICAL  CHARACTERS.  — Translucent  to  transparent.  Lustre  resinous.  Color  black, 
brown  and  orange.  Streak,  orange  to  brown.  Brittle.  H.,  4.5-5.  Sp.  gr.,  4.8-5.2. 

BEFORE  BLOWPIPE,  ETC.  —  Infusible.  Gelatinizes  with  hydrochloric  acid  before 
being  heated  by  blowpipe  but  not  after.  In  closed  tube  yields  water  and  the  orange 
variety  becomes  nearly  black  while  hot,  but  changes  to  orange  again  on  cooling. 

REMARKS.  —  Occurs  chiefly  in  Norway. 

USES.  —  Is  a  source  of  thoria,  but  less  important  than  monazite. 


CHAPTER  XXVI. 


LEAD  AND  BISMUTH  MINERALS. 
THE  LEAD  MINERALS. 


THE  minerals  described  are  : 


Metal 

Lead 

Pb 

Isometric 

Sulphide 

Galenite 

PbS 

Isometric 

Sulphantimonites 

Bournonite 

PbCuSbS, 

Orthorhombic 

Jamesonite 

Pb2Sb2S5 

Orthorhombic 

Selenide 

Clausthalite 

PbSe 

Isometric 

Oxide 

Minium 

Pb,04 

Sulphate 

Anglesite 

PbSO4 

Orthorhombic 

Phosphate 

Pyromorphite 

Pb5Cl(POi)3 

Hexagonal 

A  r  senate 

Mimetite 

Pb5Cl(AsOJ3 

Hexagonal 

Carbonate 

Cerussite 

PbCO3 

Orthorhombic 

Chromate 

Crocoite 

PbCrO, 

Monoclinic 

Vanadates 

Vanadmite 

Pb5Cl(V04)3 

Hexagonal 

Descloizite 

(Pb.Zn)(PbOH)VOi 

Orthorhombic 

Molybdate 

Wulfenite 

PbMoO4 

Tetragonal 

The  most  important  ores  of  lead  are  galenite  and  cerussite. 

The  world  uses  nearly  900,000  tons  of  lead  per  year,  of  which 
this  country,  in  1903,  produced  289,030  tons.*  Of  this  about  one 
quarter  was  soft  lead,  mainly  produced  in  Missouri  and  Kansas, 
containing  almost  no  silver  and  gold.  During  the  same  year  one 
half  of  the  total  output  of  lead  was  desilverized  ;  indeed,  it  may  be 
said  that  by  far  the  most  important  use  of  lead  ore  is  to  mix  and 
smelt  with  silver  ores,  whereby  metallic  lead  containing  silver  and 
gold  is  obtained. 

The  principal  use  of  metallic  lead  is  in  the  manufacture  of  white 
lead,  112,700  tons  being  produced  in  1903  in  the  United  States 
alone.  Large  amounts  are  also  used  for  the  preparation  of  red 
lead,  litharge,  shot,  lead  pipe  and  sheet  lead.  A  certain  amount  of 
lead  containing  antimony  is  used  in  type  and  in  alloys  for  friction- 
bearings. 

The  argentiferous  lead  ores  of  the  west,  which  ordinarily  run 
low  in  lead  are  smelted  in  blast-furnaces.  The  ore,  if  it  contains 

*  Engineering  and  Mining  Journal,  1904,  p.  4. 
255 


256  DESCRIPTIVE  MINERALOGY. 

much  sulphur,  is  roasted,  to  remove  the  sulphur  and  other  volatile 
constituents,  and  is  then  fused,  forming  a  silicate,  which  is  charged 
in  the  furnace  with  the  proper  proportions  of  fuel  and  flux  (lime- 
stone, hematite,  etc.).  The  reduction  takes  place  under  the  action 
of  the  blast  Metallic  lead,  carrying  most  of  the  silver,  is  pro- 
duced, and  if  either  sulphur  or  arsenic  is  present,  a  sulphide  (matte) 
and  an  arsenide  (speiss)  of  iron,  copper,  etc.,  will  form,  and  above 
all  these  will  float  the  slag  composed  of  the  gangue  and  the  flux. 

The  furnace  is  usually  oblong  in  section,  and  the  hearth  is  con- 
nected, by  a  channel  from  the  bottom,  with  an  outer  basin  or  well, 
so  that  the  metal  stands  at  the  same  level  in  each  and  can  easily 
be  ladled  out.  Above  the  hearth,  and  enclosing  the  smelting  zone, 
are  what  are  called  the  water  jackets,  in  which  cold  water  cir- 
culates. The  furnace  gases  pass  through  a  series  of  condensing 
chambers. 

The  matte,  speiss  and  the  dust  collected  in  the  condensing  cham- 
bers are  all  treated  for  silver,  gold,  lead,  copper,  etc.,  usually  at 
different  works.  The  metallic  lead,  or  base  bullion,  is  desilverized 
by  remelting  in  large  kettles,  raising  it  to  the  melting-point  of  zinc, 
adding  metallic  zinc  and  cooling  to  a  point  between  the  melting- 
points  of  zinc  and  lead.  The  lighter  solidified  zinc  separates,  carry- 
ing with  it  the  silver  and  gold,  and  forms  a  crust  on  the  surface  of 
the  lead,  from  which  it  is  skimmed. 

The  lead  is  further  purified  and  the  zinc,  gold  and  silver  separated 
electrolytically  or  by  distillation. 

LEAD.— Native  Lead. 

COMPOSITION. — Pb,  with  sometimes  a  little  Sb  or  Ag. 

GENERAL  DESCRIPTION.— Usually  small  plates  or  scales  or  globular  masses  em- 
bedded in  other  minerals.  Very  rarely  in  octahedrons  or  dodecahedrons. 

PHYSICAL  CHARACTERS.— Opaque.  Lustre  metallic.  Color  and  streak  lead  gray. 
H.,  1.5.  Sp.  gr.,  11.37.  Malleable. 

BEFORE  BLOWPIPE,  ETC.— Fuses  easily,  coating  charcoal  with  yellow  oxide,  and 
tinging  flame  light  blue.  Soluble  in  dilute  nitric  acid. 

GALENITE. — Galena. 

COMPOSITION. — PbS  (Pb  86.6  per  cent.),  usually  with  some  silver 
and  frequently  sulphide  of  antimony,  bismuth,  cadmium,  etc. 

GENERAL  DESCRIPTION. — A  soft,  heavy,  lead-gray  mineral,  with 
metallic  lustre  and  easy  cubical  cleavage.  Sometimes  in  crystals. 
Rarely  fine-grained  or  fibrous. 


LEAD   AND   BISMUTH  MINERALS. 


257 


CRYSTALLIZATION. —  Isometric.     Usually  the  cube,  Fig.  368,  or 
cubo-octahedron,  Fig.  369,  sometimes  octahedral  or  showing  that 

FIG.  367. 


Galenite,  Galena,  111.     N.  Y.  State  Museum. 

rare  form  the  trisoctahedron  r=  (a  :  a  :  20);   {221}  ;  Fig.  370. 
Sometimes  twinned  or  in  skeleton  crystals  or  reticulated. 


FIG.  368. 


FIG.  369. 


FIG.  370. 


Physical  Characters. — H.,  2.5. 
LUSTRE,  metallic. 
STREAK,  lead-gray. 
COLOR,  lead-gray. 


Sp.  gr.,  7.4  to  7.6. 
OPAQUE. 

TENACITY,  brittle. 
CLEAVAGE,  cubic,  very  easy. 


BEFORE  BLOWPIPE,  ETC. — On  charcoal  decrepitates  and  fuses 
easily,  yielding  in  O.  F.  a  white  sulphate  coat,  and  in  R.  F.  a  yellow 
coat  and  metallic  button  of  lead.  With  bismuth  flux,  gives  a  strong 
iodide  coat,  which  appears  chrome-yellow  on  plaster  and  greenish- 
yellow  on  charcoal.  With  soda,  yields  malleable  lead  and  a  sul- 
17 


2 $8  DESCRIPTIVE   MINERALOGY. 

phur  test.  Soluble  in  excess  of  hot  hydrochloric  acid,  from  which 
white  lead  chloride  separates  on  cooling.  Soluble  also  in  strong 
nitric  acid,  with  separation  of  sulphur  and  lead  sulphate. 

SIMILAR  SPECIES. — Characterized  by  its  cleavage,  weight  and 
.appearance,  except  in  some  fine-grained  varieties. 

REMARKS. — Galenite  is  the  common  and  parent  ore  of  lead.  It  occurs  with  other 
•sulphides,  especially  sphalerite,  pyrite  and  chalcopyrite,  with  a  gangue  of  quartz,  fluorite, 
barite  or  calcite.  Also  with  ores  of  silver  and  gold.  It  changes  easily  to  cerussite, 
anglesite  and  other  lead  minerals.  Besides  the  silver-producing  States  of  Colorado, 
Utah  and  Montana,  which  also  produce  the  most  lead,  Kansas,  Wisconsin  and  Mis- 
souri manufacture  much  soft  lead  from  their  deposits  of  galenite. 

USES. — It  is  the  chief  ore  of  lead,  and  as  it  usually  contains' 
silver,  the  silver-bearing  deposits  are  more  frequently  worked  than 
the  purer  galenite,  and  both  the  lead  and  silver  are  recovered. 

BOURNONITE. 

COMPOSITION.— PbCuSbSj,   (Pb  42.5,  Cu  13.0,  Sb  24.7,  S  19.8  per  cent.). 

GENERAL  DESCRIPTION. — A  gray  metallic  mineral,  nearer  steel-gray  than  galenite, 
and  occurring  fine-grained,  massive  and  in  thick  tabular  crystals.  More  like  tetra. 
hedrite  than  galenite  when  massive. 

CRYSTALLIZATION. — Orthorhombic.  Axes  a  :  ~b  :  ^  =  0.938:  i  :  0.897.  Common 
forms  the  pinacoids  a,  b,  c,  the  unit  domes  and  prism  d,  o,  and  m,  and  the  pyramid  u  =  (a  : 
T>  '•  */£  c)  >  {112}.  Short  prismatic  or  tabular,  with  vertically  striated  faces,  or,  in  cross, 
Fig.  372,  and  "  cog-wheel  "  twins.  Supplement  angles  mm  •=  86°  2O/,  <-<?  =  43°  43', 


FIG.  371.  FIG.  372. 


Harz.  Kapnik. 

PHYSICAL  CHARACTERS. — Opaque.  Lustre,  metallic.  Color,  steel-gray  to  nearly 
black.  Streak,  steel-gray.  H.,  2.5  to  3.  Sp.  gr.,  5.7  to  5.9.  Brittle.  Cleavages  im- 
perfect. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal,  fuses  easily,  yielding  heavy  white  sublimate. 
and  later  a  yellow  sublimate.  With  bismuth  flux  yields  strong  greenish-yellow  coat  on 
charcoal  and  a  mingling  of  chrome  yellow  and  peach  red  on  plaster.  After  sublimates 
have  formed,  the  residue  will  color  the  flame  deep  green,  or  if  moistened  with  a  drop 
of  hydrochloric  acid,  will  color  the  flame  bright  azure  blue.  Soluble  in  nitric  acid 
to  a  green  solution,  with  formation  of  a  white  insoluble  residue. 


LEAD  AND   BISMUTH  MINERALS.  259 

JAMESONITE.— Feather  Ore. 

COMPOSITION.— Pb2Sb2S5,    (Pb  50.8,  Sb  29.5,  S  19.7  per  cent.). 

GENERAL  DESCRIPTION.— Steel-gray  to  dark-gray  metallic  needle  crystals,  or  hair- 
like  and  felted ;  also  compact  and  fibrous  massive. 

PHYSICAL  CHARACTERS. — Opaque.  Lustre,  metallic.  Color,  steel-gray  to  dark- 
lead  gray.  Streak,  grayish-black.  H.,  2  to  3;  Sp.  gr.,  5.5  to  6.  Brittle. 

BEFORE  BLOWPIPE,  ETC. — Decrepitates  and  fuses  very  easily,  and  is  volatilized, 
coating  the  charcoal  white  and  yellow  as  in  bournontte.  With  bismuth  flux,  reacts  like 
bournonite.  In  closed  tube,  yields  dark-red  sublimate,  nearly  black  while  hot.  Soluble 
in  hot  hydrochloric  acid,  with  effervescence  of  hydrogen  sulphide. 

CLAUSTHALITE. 

COMPOSITION. — PbSe,    (Pb  72.4,  Se  27. 6  per  cent.).     May  contain  silver  or  cobalt. 

GENERAL  DESCRIPTION. — Bluish  gray  fine  granular  masses  of  metallic  lustre. 
Rarely  foliated.  Resembles  galenite. 

PHYSICAL  CHARACTERS. — Opaque.  Lustre,  metallic.  Color,  bluish  lead  gray 
Streak,  grayish  black.  H.,  2.5  to  3.  Sp.  gr.,  7.6  to  8.8. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  fuses  and  yields  odor  like  decayed  horse- 
radish, coats  the  charcoal  with  a  white  sublimate  with  red  border,  and  later  a  yellow 
coat  forms.  In  open  tube  gives  a  red  sublimate.  With  soda  yields  a  mass  which 
blackens  silver. 

MINIUM. 

COMPOSITION.— PbsO4,    (Pb  90.6  per  cent.). 

GENERAL  DESCRIPTION. — A  vivid  red  powder  or  loosely  compacted  mass  of  dull  or 
greasy  lustre.  Often  intermixed  with  yellow. 

PHYSICAL  CHARACTERS. — Opaque.  Bright  red.  Lustre,  dull  or  greasy.  Streak, 
orange  yellow.  II.,  2  to  3.  Sp.  gr.,  4.6. 

BEFORE  BLOWPIPE,  ETC.— Is  reduced  to  metallic  lead,  and  yields  the  characteristic 
lead  sublimates. 

REMARKS.  — The  artificial  product  is  the  red  lead  of  commerce. 

ANGLESITE. 

COMPOSITION— PbSO4,    (PbO  73.6,  SO,  26.4  per  cent). 

GENERAL  DESCRIPTION. — A  very  brittle,  colorless  or  white  mineral 
of  adamantine  lustre,  sometimes  colored  by  impurities.  Usually 
massive,  frequently  in  concentric  layers  around  a  core  of  unaltered 
galenite. 

FIG.  373.  FIG.  374. 


Phoenixville,  Pa. 


260  DESCRIPTIVE  MINERALOGY. 

CRYSTALLIZATION.  —  Orthorhombic.  Axes  a  :  b  :c  =  0.785  :  i  : 
1.289.  Crystals  vary  greatly  in  type,  but  are  rarely  twinned.  Unit 
prism  m  and  domes  such  as  n  =  (a  :  oo^  :  y2c)  ;  { 102)  ;  z  =  (a  : 
co£  :  Y^c]  ;  { 104}  ;  and  pyramids  q  =  (20,  :  b  :  c] ;  {122}  are 
frequent. 

Supplement  angles:  mm  =  76°  if;  ^2=33°  24';  cz  =  22° 
19';  ^=56°  48'. 

Optically  +  ,  with  high  indices  of  refraction  1.877,  1-882  and 
1.893  for  yellow  light.  Axial  plane  is  the  brachy  pinacoid  b. 

Physical  Characters.      H.,  3.     Sp.  gr.,  6.12  to  6.39. 

LUSTRE,  adamantine  to  vitreous.        TRANSPARENT  to  opaque. 
STREAK,  white.  TENACITY,  very  brittle. 

COLOR,  colorless,  white,  gray ;  rarely  yellow,  blue  or  green. 
CLEAVAGE,  basal  and  prismatic  (90°  and  103°  43'). 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  decrepitates  and  fuses 
easily  to  a  glassy  globule  pearly  white  on  cooling.  In  R.  F.  is  re- 
duced and  yields  metallic  lead  and  the  yellow  sublimate.  With 
soda  yields  the  sulphur  reaction.  Insoluble  in  hydrochloric  acid 
but  is  converted  into  chloride.  Slowly  soluble  in  nitric  acid. 

SIMILAR  SPECIES. — It  differs  from  the  carbonate,  cerussite,  in 
absence  of  twinned  crystals  and  of  effervescence  in  acids.  It  is 
heavier  than  barite  and  celestite,  and  yields  lead. 

REMARKS.— Anglesite  is  formed  by  the  oxidation  of  galenite.  It  alters  to  the  car- 
bonate, cerussite,  by  interchange  with  calcium  carbonate  in  solution.  It  is  found 
throughout  the  United  States  wherever  exposed  deposits  of  galenite  occur.  The  lead 
mines  of  Missouri,  Wisconsin,  Colorado,  etc.,  all  contain  this  mineral.  It  occurs  in 
large  quantities  in  Mexico  and  Australia. 

USES. — It  is  an  ore  of  lead. 


Linarite.  —  [(PbCu)OH]2SO4.     In  small,  deep  blue,  monoclinic  crystals. 

PYROMORPHITE. 

COMPOSITION.  —  Pb5Cl(PO4)3,  (PbO  82.2,  P2O.  15.7,  Cl  2.6  per 
cent.)  often  with  some  As,  Fe  or  Ca. 

GENERAL  DESCRIPTION. — Short  hexagonal  prisms  and  branch- 
ing and  tapering  groups  of  prisms  in  parallel  position.  The  color 
is  most  frequently  green,  brown,  or  gray.  Also  in  moss-like  in- 
terlaced fibers  and  masses  of  imperfectly  developed  crystals.  Less 
frequently  in  globular  and  reniform  masses. 


LEAD   AND   BISMUTH  MINERALS.  261 

CRYSTALLIZATION.  —  Hexagonal,  class   of  third  order  pyramid 

P-  Si- 

Axis  c  =  0.736.      Usual  form  prism  m  and  base  r.      Faces  m 
horizontally  striated,  sometimes  tapering. 

FIG.  375. 


I'yromorphite,  Ems,  Germany.      N.  Y.  State  Museum. 

Physical  Characters.     H.,  3.5  to  4.     Sp.  gr.,  5.9  to  7.1. 
LUSTRE,  resinous.  TRANSLUCENT  to  opaque. 

STREAK,  white  to  pale  yellow.  TENACITY,  brittle. 

COLOR,  green,  gray,  brown ;  also  yellow,  orange,  white. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  fuses  to  a  globule  which 
on  cooling  does  not  retain  its  globular  form  but  crystallizes,  show- 
ing plane  faces.  In  reducing  flame  yields  white  coat  at  a  distance 
and  yellow  coat  nearer  the  assay,  and  a  brittle  globule  of  lead. 
In  closed  tube  with  magnesium  ribbon  yields  a  phosphide  which, 
moistened  with  water,  evolves  phosphine.  With  salt  of  phos- 
phorus saturated  with  copper  oxide  yields  an  azure  blue  flame. 
Soluble  in  nitric  acid,  and  from  the  solution  ammonium  molyb- 
date  throws  down  a  yellow  precipitate. 

SIMILAR  SPECIES. — Differs  from  other  lead  minerals  in  fusing 
to  a  crystalline  globule  without  reduction. 

REMARKS  — Probably  formed  from  galenite.  Occurs  with  other  lead  minerals. 
Found  at  Phoenixville,  Pa.,  Davidson  county,  N.  C.,  Lenox,  Me.,  and  many  other 
localities. 


262 


DESCRIPTIVE  MIXERALOGY. 


MIMETITE. 

COMPOSITION.— 3Pb3(AsO4)2-f  PbCl2  or  Pb.Cl(AsO4)3,  (PbO  74.9,  As2O5  23.2,  Cl 
2.39  per  cent.),  often  with  some  replacement  by  P  or  Ca. 

GENERAL  DESCRIPTION. — Pale  yellow  to  brown  hexagonal  prisms  or  globular  groups 
of  crystals.  Sometimes  incrusting. 


FIG.  376. 


PHYSICAL  CHARACTERS.— Translucent.  Lustre,  resin- 
ous. Color,  yellow,  brown  or  white.  Streak,  white.  H., 
3.5.  Sp.  Gr.,  7.0  to  7.25,  lower  when  Ca  is  present. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  fuses  easily  and 
is  reduced  to  metallic  lead,  coating  the  coal  with  white 
and  yellow  sublimates  and  yielding  strong  arsenical  odor. 
Phosphorus,  if  present,  and  chlorine  may  be  detected  as 
in  pyromorphite. 


CERUSSITE. -White  Lead  Ore. 

COMPOSITION.— PbCO3,  (PbO,  83.5  ;  CO2,  16.5  per  cent.).  Often 
carries  silver. 

GENERAL  DESCRIPTION. — Very  brittle,  white  or  colorless  ortho- 
rhombic  crystals;  silky,  milk-white  masses  of  interlaced  fibres; 
granular,  translucent,  gray  masses  and  compact  or  earthy,  opaque 
masses  of  yellow,  brown,  etc.,  colors. 

FIG.  377. 


Cerussite,  Arizona.     N.  Y.  State  Museum. 

CRYSTALLIZATION*. — Orthorhombic.  Axes  d  :  ~b  :  c  =  0.6 10  :  i  : 
0.723.  Common  forms  :  unit  pyramid  /,  and  prism  m  and  a  series 
of  brachy  domes  such  as  x  =  (co  d  :  ~b  :  fa)  ;  (01 2} ;  u>  =  ( co  a  : 
1  :  2c]  ;  (02 1 }  and  v  =  (  co  a  :  ~b  :  3/r) ;  (03 1 } .  Frequently  twinned 


LEAD   AND    BISMUTH  MINERALS. 


263 


about  m  sometimes   yielding   six-rayed    groups  as   in   Fig.    379. 
Supplement  angles  are  mm  =  62°  46',  //  =  50°,  ww  =  1 10°  40'. 


FIG.  378. 


FIG.  379. 


Black  Hawk,  Mont. 


Transbaikal. 


Optically  — .  Axial  plane  b.  Acute  bisectrix  normal  to  c. 
High  indices  of  refraction  :  1.804,  2.076,  2.078  in  yellow  light. 

Physical  Characters.  —  H.,  3  to  3.5.     Sp.  gr.,  6.46  to  6.51. 
LUSTRE,  adamantine,  silky.          TRANSPARENT  or  translucent 
STREAK,  white.  TENACITY,  very  brittle. 

COLOR,  white,  gray,  colorless  or  colored  by  impurities. 
CLEAVAGES,  parallel  to  prism  and  brachy  dome. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal,  decrepitates,  fuses  and 
gives  a  yellow  coating,  and  finally  a  metallic  globule.  In  closed 
tube,  turns  yellow,  then  dark,  and  on  cooling  is  yellow.  Effer- 
vesces in  acids,  but  with  hydrochloric  or  sulphuric  acid  leaves  a 
white  residue. 

SIMILAR  SPECIES. — Distinguished  from  anglesite  by  efferves- 
cence in  acids  and  by  frequent  occurrence  of  twinned  crystals. 
Has  higher  specific  gravity  than  most  carbonates. 

REMARKS  — Cerussite  is  derived  from  galenite  by  the  action  of  water  containing 
carbon  dioxide.  It  may  also  be  produced  from  anglesite  by  action  of  a  solution  of 
calcium  carbonate. 

USES. — It  is  smelted  for  lead  and  silver,  and  a  process  exists  for 
the  direct  manufacture  of  white  lead  from  cerussite. 


Phosgenite.  —  Pb2C,COs.     In  transparent,  colorless  or  gray  tetragonal  crystals. 

CROCOITE. 

COMPOSITION.— PbCrO4,   (PbO,  68.9;  CrO,,  31.1  per  cent.). 

GENERAL  DESCRIPTION. — Bright  hyacinth-red  mineral,  usually  in  monoclinic  pris- 
matic crystals,  but  also  granular  and  columnar.  The  color  is  like  that  of  potassium 
dichromate. 


264 


DESCRIPTIVE  MINER ALOG Y. 


PHYSICAL  CHARACTERS. — Translucent.  Lustre,  adamantine.  t  Color,  hyacinth 
red.  Streak,  orange  yellow.  H.,  2.5  to  3.  Sp.  gr.,  5.9  to  6.1.  Sectile.  Cleavage, 
prismatic. 

BEFORE  BLOWPIPE,  ETC. — In  closed  tube,  decrepitates  violently,  becomes  dark,  but 
recovers  color  on  cooling.  Fuses  very  easily,  and  is  reduced  to  metallic  lead  with 
deflagration,  the  coal  being  coated  with  a  yellow  sublimate.  With  borax  or  S.Ph., 
forms  yellow  glasses,  which  are  bright  green  when  cold.  Soluble  in  nitric  acid  to  a 
yellow  solution.  Fused  with  KHSO4  in  closed  tube,  yields  a  dark-violet  mass,  red  on 
solidifying  and  greenish-white  when  cold,  which  distinguishes  it  from  vanadinite. 

VANADINITE. 

COMPOSITION.— 3Pb3(V04)2-PbCl2  or  Pb5Cl(VO4)3,  (PbO,  78.7; 
V2O6,  194;  Cl,  2.5  per  cent.),  often  with  P  or  As  replacing  V. 


FIG.  381 


FIG.  382. 


GENERAL  DESCRIPTION.  —  Small,  sharp,  hexagonal  prisms,  some- 
times hollow,  of  bright-red,  yellow  or  brown  color.  Also  parallel 
groups  and  globular  masses  of  crystals. 

CRYSTALLIZATION.  —  Hexagonal.  Class  third  order  pyramid, 
p.  51.  Axis  <r=o.7i2.  Simple  prism  m  with  base  <r,  or  more 
rarely  with  pyramid  p  and  third  order  pyramid  v  =  (|#  :  3*7  :  a  : 
3r);  (2 13 1},  Fig.  382. 

Physical  Characters.  —  H.,  3.     Sp.  Gr.,  6.66  to  7.23. 

LUSTRE,  resinous  on  fracture.  OPAQUE,  or  translucent. 

STREAK,  white  to  pale  yellow.  TENACITY,  brittle. 

COLOR,  deep  red,  bright  red,  yellow  or  brown. 

BEFORE  BLOWPIPE,  ETC. — Fuses  easily  on  charcoal  to  a  black 
mass,  yielding  a  yellow  sublimate  in  the  reducing  flame.  The 
residue  gives  deep-green  bead,  with  salt  of  phosphorus  in  the  re- 
ducing flame.  With  strong  nitric  acid  the  substance  becomes  deep 
red,  then  dissolves  to  a  yellow  solution.  Fused  with  KHSO4, 
yields  a  clear  yellow,  then  a  red,  and  finally  yellow  when  cold. 

USES. — It  is  the  source  of  vanadium,  for  vanadium  black  ;  for 


LEAD   AND   BISMUTH  MINERALS. 


265 


vanadium  salts,  which  are  used  as  a  mordant  in  the  manufacture 
of  the  finest  silks;  for  vanadium  bronze  and  for  vanadium  ink. 

DESCLOIZITE. 

COMPOSITION.  -  (Pb.Zn)(PbOH),V04,  (PbO,  55.4;  ZnO,  19.7 ;  V2O5,  22.7; 
H20,  2.2). 

GENERAL  DESCRIPTION. — Small  purplish-red,  brown  or  black  crystals,  forming 
a  drusy  surface  or  crust.  Also  fibrous,  massive. 

PHYSICAL  CHARACTERS.— Transparent  to  nearly  opaque.  Lustre,  greasy.  Color, 
purplish  red,  brown  or  black.  Streak,  orange  or  brown.  H.,  3.5.  Sp.  gr.,  5  9  to  6.2. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal,  fuses  to  black  mass,  enclosing  metal. 
In  closed  tube  yields  water.  Vanadium  reactions  as  in  vanadinite. 

WULFENITE. 

COMPOSITION. — PbMoO4,  sometimes  containing  Ca,  Cr.  V. 

GENERAL  DESCRIPTION. — Usually  in  thin,  square,  tabular  crys- 
tals of  yellow,  orange  or  bright  orange-red  color  and  resinous 
lustre.  Less  frequently  in  granular  masses  or  acute  pyramidal 
crystals. 

FIG.  383. 


'\Yulfenite,  Red  Cloud  Mine,  Arizona.     Foote  Mineral  Co. 

CRYSTALLIZATION.  —  Tetragonal.     Class  of  third  order  pyramid, 
p.  41.      Axis  c  —  1.577.      Usually  the   base  c  with  the  pyramid 


FIG.  384. 


FIG.  385. 


FIG.  386. 


266  DESCRIPTIVE  MINERALOGY. 

e  =  (a  \  co  a  \  \c]  ;    { 102} .      More  rarely  the  unit  pyramid  /  and  a 
third  order prism/=  (a  :  \a  :  co  c} ;  {320}.      Angles  =38°  15', 

//  =  80°  22'. 

Optically  — . 
Physical  Characters.     H.,  3.     Sp.  gr.,  6.7  to  7. 

LUSTRE,  resinous  or  adamantine.  TRANSLUCENT. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  wax  yellow,  bright  red,  brown,  rarely  green. 
CLEAVAGE,  pyramidal. 

BEFORE  BLOWPIPE,  ETC. — Fuses  easily  on  charcoal,  giving  yel- 
low coat  and  finally  a  metallic  globule.  In  salt  of  phosphorus 
dissolves  to  a  bead,  which  is  bright  green  in  R.  F.  In  borax, 
yields  a  colorless  bead  in  O.  F.,  which  is  made  brown  to  black  in 
R.  F.  Partially  soluble  in  strong  hydrochloric  acid  to  a  green 
liquid.  If  the  solution  is  greatly  diluted,  cooled  and  tin  added, 
it  becomes  deep  blue  and  finally  brown.  A  similar  test  may  be 
obtained  either  by  boiling  in  porcelain  with  strong  sulphuric  acid 
and  adding  alcohol,  or  by  fusing  in  platinum  with  KHSO4,  dis- 
solving in  water  and  boiling  with  tin  or  zinc. 

REMARKS. — Wulfenite  occurs  with  other  lead  minerals,  especially  vanadinite  and 
pyromorphite.  It  is  found  in  many  localities  in  New  Mexico  and  Arizona ;  in  the 
lead  regions  of  Wisconsin  and  Missouri;  at  Phoenixville,  Pa.;  Inyo  County,  Cal. ; 
Southampton,  Mass.,  and  many  other  places,  always  associated  with  other  ores  of  lead. 

THE  BISMUTH  MINERALS. 

The  minerals  described  are  : 

Metal  Bismuth  Bi  Hexagonal 

Sulphide  Bismuthinite  Bi2S3  Orthorhombic 

Telluride  Tetradymile  Bi2(Te.S)s  Hexagonal 

Carbonate  Bismutite  ( BiO )  jCO3.  H.2O 

Oxide  Bismite  Bi2Os  Orthorhombic 

Bismuth  is  also  found  intimately  mixed  with  other  minerals,  as 
with  tin  ore  in  Bolivia  ;  cobalt  ore  in  Saxony  and  gold-bearing 
magnetite  in  Queensland,  Australia. 

The  principal  source  of  bismuth  is  the  native  metal ;  it  is,  how- 
ever, extracted  from  the  other  minerals,  and  to  a  considerable  ex- 
tent from  the  hearths  and  last  products  of  oxidation  of  lead  cupella- 
tion.  The  manufacture  is  practically  all  in  Germany  and  England, 
the  latter  country  reducing  Australian  and  Bolivian  ores.  The 
quantity  produced  per  year  is  small. 


LEAD   AND   BISMUTH  MINERALS.  267 

The  uses  of  bismuth  are  chiefly  dependent  upon  its  property  of 
forming  easily  fusible  alloys  with  other  metals,  especially  tin,  lead, 
and  cadmium.  These  alloys  expand  in  cooling,  and  are  there- 
fore used  in  reproducing  woodcuts,  in  making  safety  plugs  for 
boilers,  etc.  The  salts  of  bismuth  have  numerous  uses  in  medicine 
and  in  the  arts,  are  used  in  calico  printing,  cosmetics,  and  in 
making  glass  of  high  refractive  power,  and  also  to  impart  lustre 
to  porcelain. 

Bismuth  was  formerly  obtained  from  the  native  metal  by  simply 
heating  in  a  closed,  inclined  vessel,  the  liquid  metal  flowing  out. 
This  method  was  wasteful,  as  any  bismuth  present  as  sulphide  or 
telluride  was  not  obtained  while  much  of  the  metal  was  lost.  In 
Saxony  where  most  of  the  bismuth  of  the  world  is  produced  the 
ores  are  first  roasted  to  free  them  from  sulphur,  arsenic  and  other 
volatile  constituents.  After  roasting  they  are  smelted  in  crucibles 
with  iron,  charcoal  and  slag,  the  melted  bismuth  settling  out  in 
the  bottom  of  the  crucible ;  or  the  roasted  ores  may  be  treated 
with  strong  hydrochloric  acid  (i  :  i)  which  dissolves  the  bismuth 
and  from  which  it  is  precipitated  as  oxychloride  by  the  addition  of 
water.  The  metal  may  be  further  purified  electrolytically.  When 
bismuth  is  found  to  be  present  in  the  cupellation  of  lead  ore,  it  is 
recovered  by  saving  the  last  products  of  oxidation  and  the  hearth 
of  the  furnace,  grinding  these  and  treating  them  with  hot  strong 
hydrochloric  acid.  After  settling  and  cooling  the  liquid  is  siphoned 
off  and  diluted  with  water,  by  which  a  precipitate  of  the  oxychlo- 
ride is  produced,  which,  after  being  dissolved  in  hydrochloric  acid 
and  reprecipitated  some  two  or  three  times  to  separate'lead  chloride, 
is  easily  reduced  to  metallic  bismuth  by  fusion  with  soda,  or  lime, 
charcoal  and  a  silicious  slag. 

BISMUTH.  —  Native   Bismuth.  FIG.  387. 

COMPOSITION.  —  Bi,  often  alloyed  with  As 
or  impure  from  S  or  Te. 

GENERAL  DESCRIPTION.  —  A  brittle  silver- 
white  mineral  with  a  reddish  tinge,  usually 
disseminated  through  the  gangue  in  branch- 
ing lines,  Fig.  387,  or  in  isolated  grains 
or  lumps.  Rarely  in  indistinct  hexagonal 

crystals.  Schneeberg,  Saxony. 


268  DESCRIPTIVE  MINERALOGY. 

Physical  Characters.     H.,  2  to  2.5.     Sp.  gr.,  9.7  to  9.83. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  silver  white.  TENACITY,  sectile  to  brittle. 

COLOR,  reddish  silver  white. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  fuses  easily  and  volatilizes 
completely,  coating  the  charcoal  with  a  yellow  sublimate.  With 
bismuth  flux  forms  a  chocolate  brown  and  red  coating  which  is  best 
seen  on  plaster,  and  which  is  changed  by  action  of  ammonia  fumes 
to  red  and  orange.  Soluble  in  strong  nitric  acid  from  which  solu- 
tion water  will  precipitate  a  white  basic  salt. 

SIMILAR  SPECIES. — Bismuth  is  characterized  by  its  silver  streak, 
reddish  tinge,  and  arborescent  structure. 

REMARKS. — Bismuth  occurs  in  crystalline  rocks  and  clay  slate  associated  with  ores  of 
cobalt,  nickel,  silver,  gold,  lead  and  zinc,  also  with  molybdenite,  wolframite,  scheelite. 
The  native  metal  is  not  found  in  any  quantity  in  the  United  States,  although  obtained 
at  Monroe,  Ct.,  n  Colorado,  and  in  South  Carolina.  The  most  celebrated  foreign 
localities  are  Schneeberg  in  Saxony  and  other  places  both  in  Saxony  and  Bohemia. 
Found  also  at  Copiapo,  Chili ;  in  Bolivia,  Sweden,  Norway,  and  in  South  Australia. 

USES. — It  is  a  source  of  commercial  bismuth  and  of  salts  of  bis- 
muth. 

BISMUTHINITE. 

COMPOSITION.— Bi2S3)    (Bi  81.2,  S  18.8  per  cent.).     May  contain  Cu  or  Fe. 

GENERAL  DESCRIPTION. — A  lead  gray  mineral  of  metallic  lustre  usually  occurring 
in  foliated  or  fibrous  masses,  or  in  groups  of  long  needle-like  orthorhombic  crystals. 

PHYSICAL  CHARACTERS. — Opaque.  Lustre,  metallic.  Color,  lead  gray  or  lighter, 
often  with  yellow  tarnish.  Streak,  lead  gray.  H.,  2.  Sp.  gr.,  6.4  to  6.5.  Slightly 
sectile. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  yields  some  sulphur,  fuses  easily  with  spirt- 
ing, and  coats  the  coal  with  white  and  yellow  sublimates.  Yields  the  characteristic  bis- 
muth reactions  with  bismuth  flux  and  with  nitric  acid  as  described  under  bismuth. 
With  soda  gives  sulphur  reaction. 


Aikinite.  —  BiPbCuSs.     Needles  of  dark  gray  color  embedded  in  quartz. 

TETRADYMITE. 

COMPOSITION. — Bi2(Te.S)3  or  BiTeS.     Either  an  alloy  or  a  telluride  of  bismuth. 

GENERAL  DESCRIPTION. — Very  soft,  flexible,  foliated  masses  of  steel-gray  color  and 
bright  metallic  lustre,  or  small  indistinct  rhombohedral  crystals.  Will  mark  paper  like 
graphite. 

PHYSICAL  CHARACTERS,  ETC. — Opaque.  Lustre,  metallic.  Color,  pale  steel-gray. 
Streak,  gray.  H.,  1.5  to  2.  Sp.  gr.,  7.2  to  7.6.  Flexible  in  laminae.  Cleavage,  basal. 


LEAD   AND   BISMUTH  MINERALS.  •      269 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  fuses  easily  and  is  completely  volatilized, 
yielding  a  white  fusible  sublimate,  followed  by  a  yellow  sublimate.  The  flame  during 
fusion  is  colored  blue.  The  white  sublimate  if  placed  on  procelain  and  moistened 
with  concentrated  sulphuric  acid  becomes  rose  colored.  If  dropped  into  boiling  con- 
centrated sulphuric  acid  a  deep  violet  color  is  produced. 

BISMUTITE. 

COMPOSITION.  —  (BiO).,COj,  H2O,  variable. 

GENERAL  DESCRIPTION.  —  A  light  colored  incrustation  or  earthy  mass  or  powder. 

PHYSICAL  CHARACTERS.  —  Opaque.  Lustre,  dull  or  vitreous.  Color,  white,  green 
and  yellow.  Streak,  colorless  to  greenish.  H.,  4-4.5;  Sp.  gr.,  6.9-7.7.  Tenacity, 
brittle. 

BEFORE  BLOWPIPE,  ETC.  —  Fuses  easily  on  charcoal,  giving  a  yellow  coat  and  in 
R.  F.  a  metallic  globule  which  completely  volatilizes.  With  bismuth  flux  on  plaster 
gives  brown  and  red  coat.  Yields  water  in  closed  tube  and  decrepitates.  Soluble  with 
effervescence  in  strong  HC1,  and  on  dilution  with  much  "water  the  white  oxychloride  of 
bismuth  is  precipitated. 

USES.  —  Is  an  important  ore  of  bismuth. 

REMARKS.  —  It  is  usually  associated  with  metallic  bismuth  or  the  sulphide  and  occurs 
at  Brewer'  Mine,  S.  C.,  Phoenix,  Arizona,  Inyo  Co.,  Cal. 

BISMITE.  —  Bismuth  Ochre. 

COMPOSITION.  —  Bi2O3,  Bi  89.6  per  cent,  when  pure. 

GENERAL  DESCRIPTION.  —  A  yellowish  or  gray  powder  or  earthy  mass. 

PHYSICAL  CHARACTERS.  —  Opaque.  Color,  grayish,  greenish  or  yellowish  white. 
Lustre,  dull. 

BEFORE  BLOWPIPE,  ETC.  —  As  for  bismutite  but  does  not  effervesce  with  acids  nor 
yield  water  in  closed  tube. 

USES.  —  It  is  the  source  of  some  bismuth. 


CHAPTER   XXVII. 

ARSENIC,  ANTIMONY,  URANIUM   AND    MOLYBDENUM 
MINERALS. 

THE    ARSENIC    MINERALS. 

THE  minerals  described  are  : 

Metal  Arsenic  As  Hexagonal 

Sulphides  Orpiment  As2S3  Orthorhombic 

Realgar  As2S2  Monoclinic 

The  principal  sources  of  metallic  arsenic  and  white  arsenic  are 
not  the  above  mentioned  minerals,  but  the  arsenides  and  arseno- 
sulphides  of  iron,  cobalt  and  copper.  The  greater  part  of  the 
world's  supply  of  arsenic  and  its  compounds  comes  from  Cornwall, 
England ;  Freiberg,  Saxony ;  and  from  Prussia. 

Metallic  arsenic  is  ordinarily  produced  by  sublimation  from  a 
mixture  of  the  oxide  and  charcoal,  but  may  be  produced  by  sub- 
limation at  a  high  heat  directly  from  arsenopyrite  out  of  contact 
with  air.  It  is  a  constituent  of  some  useful  alloys,  shot  metal 
being  the  chief. 

The  poisonous  oxide  commonly  known  as  arsenic  or  white  arsenic, 
is  produced  in  large  quantities  by  the  roasting  of  arsenopyrite  and 
other  arsenical  ores  and  as  a  by-product  in  the  preparation  of  tin, 
silver,  nickel  and  cobalt.  It  is  used  in  dyeing,  in  medicine,  in  sheep 
washing,  in  calico  printing,  as  a  preservative  for  timber  and  for 
natural  history  specimens,  in  the  manufacture  of  fly  paper,  and  rat 
poisons,  and  in  glass  manufacture.  Many  important  coloring 
matters  as  well  as  the  artificial  red  and  yellow  sulphides  are  com- 
mercial products.  Paris  green  is  an  arsenate  of  copper  extensively 
used  as  an  insecticide.  The  production  of  arsenic  in  1903  in  the 
United  States  was  590  tons.* 

ARSENIC.— Native  Arsenic. 

COMPOSITION. — As,  generally  withs^me  Sb  and  sometimes  with  Bi  or  a  little  Co,  Ni, 
Fe,  Ag  or  Au. 

*  Eng.  and  Min.  Jour.,  1904,  p.  4. 

270 


ARSENIC,    ANTIMONY,    ETC.,    MINERALS.  2/1 

GENERAL  DESCRIPTION.— A  tin- white  metal,  tarnishing  almost  black.  Usually 
granular,  massive,  with  reniform  surfaces.  Can  frequently  be  separated  in  concentric 
layers.  Rarely  found  in  needle-like  crystals. 

PHYSICAL  CHARACTERS. — Opaque.  Lustre,  nearly  metallic.  Color,  tin  white,  tar- 
nishing nearly  black.  Streak,  tin  white.  H.,  3.5.  Sp.  gr.,  5.63  to  5.73.  Brittle. 
Granular  fracture. 

BEFORE  BLOWPIPE,  ETC.-^On  charcoal,  volatilizes  without  fusion,  yielding  strong 
garlic  odor,  white  fumes,  crystalline  white  sublimate  and  pale  blue  flame.  May  leave 
a  residue  of  impurities. 

REALGAR. 

COMPOSITION.— As2S2,    (As,  70,1  ;  S,  29.9  per  cent.). 

GENERAL  DESCRIPTION. — A  soft,  orange-red  mineral,  of  resinous 
lustre,  usually  occurring  in  translucent,  granular  masses,  but  also 
compact  and  in  transparent  monoclinic  crystals. 

Physical  Characters.     H.,  1.5  to  2.     Sp.  gr.,  3.4  to  3.6. 
LUSTRE,  resinous.  TRANSLUCENT  to  transparent. 

STREAK,  orange  red.  TENACITY,  slightly  sectile. 

COLOR,  aurora  red,  becoming  orange  yellow  on  long  exposure. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal,  fuses  easily,  burns  with 
a  blue  flame,  yields  white  fumes,  with  garlic  odor  and  also  odor 
of  sulphur  dioxide  and  is  volatilized  completely.  In  closed  tube 
yields  red  sublimate.  Soluble  in  nitric  acid,  with  separation  of 
sulphur.  Soluble  also  in  potassium  hydroxide  from  which  hy- 
d  ochloric  acid  precipitates  yellow  flakes. 

REMARKS.— Realgar  is  found  with  orpiment,  arsenolite,  galenite,  argentite,  etc.,  and 
is  formed  both  by  sublimation  and  by  deposition  from  water.  Realgar  is  obtained 
mainly  from  abroad,  notably  from  Hungary  and  the  island  of  Borneo.  Deposits  are 
known  in  Utah,  California  and  Wyoming. 

USES. — The  artificial  sublimate  is  used  in  fireworks  and  for  sig- 
nalling, in  the  form  of  "  white  Indian  fire."  It  also  is  used  as  a 
pigment. 

ORPIMENT. 

COMPOSITION. — As2Ss,    (As,  61  ;  S,  39  per  cent.). 

GENERAL  DESCRIPTION. — Lemon-yellow,  foliated  masses,  which 
cleave  into  thin,  pearly,  flexible  scales,  and  also  granular  masses 
like  yolk  of  hard-boiled  eggs.  Less  frequently  as  reniform  crusts 
and  imperfect  orthorhombic  crystals. 


272  DESCRIPTIVE  MINERALOGY. 

Physical  Characters.     H.,  1.5  to  2      Sp.  gr.,  3.4  to  3.6. 
LUSTRE,  resinous  or  pearly.     TRANSLUCENT  to  nearly  opaque. 
STREAK,  lemon  yellow.  TENACITY,  slightly  sectile. 

COLOR,  lemon  yellow.  CLEAVAGE,  in  plates  or  leaves. 

BEFORE  BLOWPIPE,  ETC. — As  for  realgar,  except  that  the  sub- 
limate in  closed  tube  is  yellow. 

REMARKS. — Probably  generally  formed  by  sublimation,  but  is  also  deposited  from 
hot  water,  and  formed  by  alteration  of  realgar  in  air  and  sunlight.  It  occurs  with 
realgar,  arsenic,  arsenolite,  etc.  Obtained  mainly  from  several  Hungarian  localities, 
from  Borneo,  and  from  Kurdistan,  Turkey.  Found  in  powder  at  Edenville,  N.  Y.,  and 
massive  in  Wyoming,  Utah  and  Nevada. 

USES. — The  artificial  material  is  used  in  dyeing  to  reduce  indigo, 
and  in  tanning,  as  a  constituent  with  potash  and  lime,  to  remove 
hair  from  the  skins  and  as  a  pigment. 

THE    ANTIMONY    MINERALS. 

The  minerals  described  are  : 

Metal  Antimony  Sb  Hexagonal 

.    Sulphides  Stibnite  Sb2S3  Orthorhombic 

Kermesite  Sb2S2O  Monoclinic 

Oxide  Valentinite  Sb2O3  Orthorhombic 

Lead  ores  also  frequently  contain  antimony. 

The  only  commercially  important  antimony  mineral  is  the  sul- 
phide, a  little  of  which  is  used  as  sulphide  in  vulcanizing  rubber, 
and  in  safety  matches,  percussion  caps,  fireworks,  etc.,  but  is 
chiefly  important  as  a  source  of  the  metal.  In  1903  this  country 
produced  3 ,400  tons  *  of  metallic  antimony,  and  used  about  twice 
that  quantity,  chiefly  in  preparing  type  and  stereotype  metal  and 
other  alloys.  Type  metal  is  now,  however,  principally  produced 
from  antimonial  lead  obtained  as  a  by-product  in  refining  base 
bullion. 

France,  Italy,  Mexico  and  Japan  are  at  present  the  chief  pro- 
ducers. 

In  smelting,  the  ore  is  heated  and  the  melted  sulphide  drained 
off.  The  sulphide  may  then  be  roasted,  forming  the  oxide,  which 
is  easily  reduced  by  fusion  with  charcoal,  or  more  frequently  the 
sulphide  is  mixed  with  wrought-iron  scraps  and  salt,  placed  in  a 

* Eng.  and  Min.  Jour.,  1904,  p.  3. 


ARSENIC,    ANTIMONY,    ETC.,    MINERALS. 


273 


crucible    or   furnace    and    fused.     The   iron    combines    with    the 
sulphur  and  the  metallic  antimony  settles  to  the  bottom. 

The  metal  produced  by  either  method  is  usually  refined  by 
smelting  with  sodium  carbonate  and  a  little  antimony  sulphide, 
followed  by  two  fusions  with  sodium  carbonate  alone. 

ANTIMONY.-Native  Antimony. 

COMPOSITION.— Sb,  sometimes  with  As,  Fe  or  Ag. 

GENERAL  DESCRIPTION.— A  very  brittle,  tin-  white  metal,  usually  massive,  with  fine, 
granular,  steel-like  texture  or  lamellar  or  radiated.  Very  rarely  in  rhombohedral 
crystals  or  complex  groups. 

PHYSICAL  CHARACTERS. — Opaque.  Lustre,  metallic.  Color,  tin  white.  Streak 
tin  white.  H.,  3  to  3.5.  Sp.  gr.,  6.5  to  6.72.  Very  brittle. 

BEFORE  BLOWPIPE,  ETC.— Fuses  very  easily,  colors  the  flame  pale  green,  gives 
copious  white  fumes,  which  continue  to  form  as  a  thick  cloud  after  cessation  of  blast, 
and  often  yield  a  crust  of  needle-like  crystals. 


STIBNITE.— Gray  Antimony. 

COMPOSITION. — Sb2S3,  (Sb  71.8,  S  28.2  per  cent).  Sometimes 
contains  silver  or  gold. 

GENERAL  DESCRIPTION.  — A  lead-gray  mineral  of  bright  metallic 
lustre,  occurring  in  imperfectly  crystallized  masses,  with  columnar 
or  bladed  structure ;  less  frequently  in  distinct,  prismatic,  ortho- 
rhombic  crystals  or  confusedly  interlaced  bunches  of  needle-like 
crystals ;  also  in  granular  to  compact  masses. 

FIG.  388. 


Stibnitr,    |-'c]>oh;in\.i,    limitary.       ('olmnhiu  I  nix  i-r.sity. 


274  DESCRIPTIVE  MINERALOGY. 

CRYSTALLIZATION.  —  Orthorhombic.  Axes  d  :  J  :  c  =  0.993  :  i  : 
1.018.  Prismatic  forms,  often  bent  and  curved  or  in  divergent 
groups.  The  vertical  planes  are  striated  longitudinally. 

Common  forms  :  unit  prism  in,  unit  pyramid  /  and  pyramid 
s  =  (a  :  b\  Y^c] ;  {113}.  Supplement  angles  mm  =  89°  34'  ;  pp 
=  70°  48';  ^=35°  36'. 

Physical  Characters.     H.,  2.     Sp.  gr,  4.52  to  4.62. 

LUSTRE,  metallic.  OPAQUE. 

STREAK,  lead  gray.  TENACITY,  brittle  to  sectile. 

COLOR,  lead  gray,  often  with  black  or  iridescent  tarnish. 

CLEAVAGE,  easy,  parallel  to  brachy  pinacoid,  yielding  slightly 
flexible,  blade-like  strips. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal,  fuses  very  easily,  yielding 
the  same  dense  sublimate  as  antimony.  The  odor  of  sulphur  di- 
oxide may  also  be  noticed.  On  charcoal,  with  soda,  yields  sulphur 
test.  In  closed  tube  fuses  easily,  yields  a  little  sulphur  and  a  dark 
sublimate  which  is  brownish  red  when  cold. 

Soluble  completely  in  strong  boiling  hydrochloric  acid,  with  evo- 
lution of  H2S,  with  precipitation  of  white  basic  salt  on  addition  of 
water  and  after  dilution  an  orange  precipitate  on  addition  of  H2S. 
Strong  nitric  acid  decomposes  stibnite  into  white  Sb2O5  and  S. 
Strong  hot  solution  of  KOH  colors  stibnite  yellow  and  partially 
dissolves  it.  From  the  solution  hydrochloric  acid  will  throw  down 
an  orange  precipitate. 

SIMILAR  SPECIES. — Differs  from  galenite  in  cleavage,  and  from 
all  sulphides  by  ease  of  fusion  and  cloud-like  fumes. 

REMARKS. — Stibnite  occurs  in  veins  with  other  antimony  minerals  formed  from  it, 
also  with  cinnabar,  sphalerite,  siderite,  etc.  Large  deposits  of  stibnite  occur  at  Love- 
locks,  Bernier  and  Austin,  Nevada  ;  at  Kingston,  Idaho  ;  at  San  Emidio,  California; 
in  Arkansas,  in  Utah,  in  Nova  Scotia  and  in  New  South  Wales.  The  most  celebrated 
deposit,  however,  is  that  in  Shikoku,  Japan,  from  which  the  very  finest  crystals  and 
groups  are  obtained. 

USES. — It  is  the  chief  source  of  antimony  and  its  artificial  pig- 
ment and  pharmaceutical  preparations.  In  the  natural  state  it  is 
used  in  safety  matches  and  percussion  caps,  in  fireworks  and  in 
rubber  goods. 


ARSENIC,    ANTIMONY,    ETC.,    MINERALS.  275 

KERMESITE.-Red  Antimony. 

COMPOSITION —SbjSjO  or  2Sb2S3-Sb2O3,    (Sb  75.0,  S  20.0,  O  5.0  per  cent.). 
GENERAL  DESCRIPTION.— Fine  hair-like  tufts  of   radiating  fibers  and  needle-like 
crystals,  of  a  deep  cherry-red  color  and  almost  metallic  lustre. 

PHYSICAL  CHARACTERS. — Nearly  opaque.  Lustre,  adamantine.  Color,  dark  cherry 
red.  Streak,  brownish  red.  H.,  I  to  1.5.  Sp.  gr.,  4.5  to  4.6.  Sectile  and  in  thin 
leaves  slightly  flexible. 

BEFORE  BLOWPIPE,  ETC. — As  for  stibnite. 

REMARKS. — Kermesite  results  from  partial  oxidation  of  stibnite.  Extensive  de- 
posits exist  at  Pereta,  Tuscany. 

VALENTINITE. 

COMPOSITION.  —  Sb2O3,  (Sb,  83.3  per  cent.). 

GENERAL  DESCRIPTION.  —  Small  white  flat  crystals  ( orthorhombic )  or  radiating 
groups  of  silky  lustre  and  white  or  gray  color.  Also  in  spheroidal  masses  with  radiated 
lamellar  structure. 

PHYSICAL  CHARACTERS.  —Translucent.  Lustre,  adamantine  or  silky.  Color,  white, 
gray,  pale  red.  Streak,  white.  H.,  2.5  to  3.  Sp.  gr.,  5.57. 

BEFORE  BLOWPIPE,  ETC.  —  Fuses  easily,  coating  the  charcoal  with  white  oxide.  In 
R.  F.  is  reduced,  but  again  oxidizes  and  coats  the  coal,  coloring  the  flame  green.  Solu- 
ble in  hydrochloric  acid. 

REMARKS.  —  Formed  by  oxidation  and  decomposition  of  stibnite  and  other  ores  of 
antimony. 

Senarmontite.  —  SbaO3.     In  pearl  colored  isometric  octahedra. 

THE    URANIUM    MINERALS. 

The  minerals  described  are  : 

Uranate  Uraninite  Uranyl  uranate  Isometric 

Vanadate  Carnotite  Uranyl  vanadate 

Phosphates  Antunite  Ca(UOa)2(PO4)2  8H2O         Orthorhombic 

Torbernite  CUJUO^JPOJ,  8H2O         Tetragonal 

The  metal  uranium  has  a  limited  use  in  uranium  steel,  as  a  small 
percentage  of  uranium  increases  the  elasticity  and  hardness  of  or- 
dinary steel.  In  1901  the  United  States  produced  375  tons  *  of 
uranium  ore. 

A  few  tons  of  sodium  uranate,  commercially  known  as  uranium 
yellow,  are  used  each  year  in  coloring  glass  yellow  with  a  greenish 
reflex,  and  in  coloring  porcelain  orange  or  black.  A  small  amount 
is  used  in  photography  and  in  the  manufacture  of  uranium  salts  im- 
portant in  the  laboratory. 

Recently  an  unusual  interest  has  been  developed  in  uranium 
minerals  from  the  discovery  of  the  new  radioactive  element  radium 
in  uraninite.  It  has  also  been  proved  to  be  present  in  many  other 

*  Mineral  Industry,  XI.,  1902,  558. 


276  DESCRIPTIVE  MINERALOGY. 

uranium  minerals  and  is  probably  present  in  all.  Many  tons  of 
uraninite  have  been  worked  over  to  obtain  a  few  grams  of  impure 
radium  chloride,  the  remarkable  properties  of  which  are  being 
widely  studied.  It  seems  probable  that  there  is  here  the  first 
known  instance  of  the  decomposition  of  the  chemical  atom,  for 
radium  gives  off  helium  apparently  as  a  decomposition  product, 
and  with  the  evolution  of  an  amount  of  energy  far  beyond  any 
previous  conception.  It  also  is  continually  throwing  off  emanations 
or  rays  which  affect  a  photographic  plate  and  discharge  an  electro- 
scope. Some  of  these  too  are  of  a  material  character.  Still  years 
must  elapse  before  any  loss  of  weight  can  be  detected  by  the  most 
delicate  balance.  Uranium  minerals  in  general  are  radioactive 
undoubtedly  from  the  radium  they  contain. 

URANINITE.— Pitch  Blende. 

COMPOSITION. — A  uranate  of  UO2,  Pb,  etc.,  and  may  contain  Ca, 
N,  Th,  Zr,  Fe,  Cu,  Bi,  etc. 

GENERAL  DESCRIPTION. — A  black  massive  mineral  of  botryoidal 
or  granular  structure  and  pitch-like  appearance.  Rarely  in  small 
isometric  crystals. 

Physical  Characters.     H.,  5.5.     Sp.  gr.,  5  to  9.7. 
LUSTRE,  pitch-like,  submetallic.  OPAQUE. 

STREAK,  gray,  olive  green,  dark  brown.        TENACITY,  brittle. 
COLOR,  some  shade  of  black. 

BEFORE  BLOWPIPE,  ETC. — Infusible  or  very  slightly  fused  on 
edges,  sometimes  coloring  the  flame  green  from  copper.  On  char- 
coal with  soda  may  yield  reaction  for  lead,  arsenic  and  sulphur.  In 
borax  yields  a  green  bead  made  enamel  black  by  flaming.  Soluble 
in  nitric  acid  to  a  yellow  liquid  from  which  ammonia  throws  down 
a  bright  yellow  precipitate. 

SIMILAR  SPECIES. — The  appearance  and  streak  are  frequently 
sufficient  distinctions.  The  bead  tests  are  characteristic. 

REMARKS. — Uraninite  occurs  both  in  granitic  rocks  and  in  metallic  veins.  It  is 
frequently  associated  with  minerals  resulting  from  its  decomposition  and  with  metallic 
ores.  It  is  mined  at  Joachimstal,  Bohemia,  from  whence  the  principal  supply  is 
obtained.  It  occurs  in  Jefferson  and  Gilpin  counties,  Colorado,  having  been  mined  at 
Central  City  and  is  found  also  in  some  quantity  in  Mitchell  county,  N.  C.,  at  Marietta, 
S.  C.,  in  Texas,  and  in  the  Black  Hills  of  South  Dakota. 


ARSENIC,    ANTIMONY,    ETC.,    MINERALS.  277 

USES. — Uraninite  is  the  chief  source  of  the  uranium  salts  used 
in  painting  on  porcelain  and  in  the  manufacture  of  a  fluorescent 
glass  of  yellowish-green  color.  It  is  the  source  from  which  all  the 
radium  chloride  and  bromide  so  far  produced  has  been  obtained. 


Carnotite.  —  An  impure  uranyl  vanadate  occurring  as  a  canary  yellow,  ocherous  ma- 
terial in  Colorado.  It  contains  a  high  percentage  of  uranium  and  is  a  possible  source 
of  radium. 

AUTUNITE— Lime  Uranite. 

COMPOSITION;— Ca(U02)2(PO<)2  +  8H2O,  (UO3  62.7,  CaO  6.1,  P2O5 15.5,  H,O  15.7 
per  cent.). 

GENERAL  DESCRIPTION. — Nearly  square  (90°  43')  orthorhombic  plates  of  bright 
yellow  color  and  pearly  lustre,  or  in  micaceous  aggregates. 

PHYSICAL  CHARACTERS. — Translucent.  Lustre,  pearly  on  base.  Color,  lemon  to 
sulphur  yellow.  Streak,  pale  yellow.  H.,  2  to  2.5.  Sp.  gr.,  3.05  to  3.19.  Brittle. 
Cleavage  basal. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  fuses  with  intumescence  to  a  black  crystal- 
line globule.  With  salt  of  phosphorus  or  borax  in  the  reducing  flame  yields  a  green 
bead.  Dissolves  in  nitric  acid  to  a  yellow  solution. 

TORBERNITE.— Copper  Uranite. 

CoMPOSiTiON.-Cu(U02)j(POJ,  4-  8H20,  (UO3  61.2,  CuO  8.4,  PaO5  15.1,  HaO 
15.3  per  cent.). 

GENERAL  DESCRIPTION. — Thin  square  tetragonal  plates  of  bright  green  color  and 
pearly  lustre.  Sometimes  in  pyramids  or  micaceous  aggregates. 

PHYSICAL  CHARACTERS. — Translucent.  Lustre,  pearly.  Color,  emerald  to  grass 
green.  Streak,  pale  green.  H.,  2  to  2.5.  Sp.  gr.,  3.4  to  3.6.  Brittle. 

BEFORE  BLOWPIPE,  ETC. — Fuses  easily  to  a  black  mass  and  colors  the  flame  green. 
In  borax  yields  a  green  glass  in  O.  F.,  which  becomes  opaque  red  in  R.  F.  Soluble 
in  nitric  acid  to  a  yellowish  green  solution. 


THE  MOLYBDENUM  MINERALS. 

The  minerals  described  are  : 

Sulphide  Molybdenite  MoS,  Hexagonal 

Oxide  Molybdite  MoO,  Orthorhombic 

Besides  these  molybdenum  occurs  as  the  acid  constituent  of 
wulfenite  described  on  page  265. 

The  metal  has  an  increasing  use  in  the  production  of  an  alloy 
with  steel.  Its  chief  important  compounds  are  sodium  molybdate, 
used  to  impart  a  blue  color  to  pottery  and  in  dyeing  silks  and 
woolens,  and  molybdic  acid  from  which  useful  chemical  reagents' 
are  prepared  in  the  laboratory. 


2/8  DESCRIPTIVE  MINERALOGY. 

MOLYBDENITE. 

COMPOSITION. — MoS2,    (Mo  60.0,  S  40.0  per  cent.). 

GENERAL  DESCRIPTION. — Thin  graphite-like  scales  or  foliated 
masses  of  metallic  lustre  and  bluish  gray  color,  easily  separated 
into  flexible  non-elastic  scales.  Sometimes  in  tabular  hexagonal 
forms  and  fine  granular  masses.  Soft,  unctuous  and  marks  paper. 

Physical  Characters.     H.,  I  to  1.5.     Sp.  gr.,  4.6  to  4.9. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  greenish.*  TENACITY,  sectile  to  malleable. 

COLOR,  bluish  lead  gray.  CLEAVAGE,  basal. 

BEFORE  BLOWPIPE,  ETC. — In  forceps  infusible,  but  at  high  heat 
colors  the  flame  yellowish  green.  On  charcoal  gives  sulphurous 
odor  and  slight  sublimate,  yellow  hot,  white  cold,  and  deep  blue 
when  flashed  with  the  reducing  flame.  Soluble  in  strong  nitric 
acid  and  during  solution  on  platinum  it  is  luminous.  With  sul- 
phuric acid  yields  a  blue  solution.  In  salt  of  phosphorus  and 
borax  yields  characteristic  molybdenum  reactions. 

SIMILAR  SPECIES. — Differs  from  graphite  in  streak  and  blowpipe 
reactions.  May  usually  be  distinguished  by  its  lighter  bluish  gray 
color. 

REMARKS.  —  Occurs  usually  in  crystalline  rocks,  and  is  not  readily  altered.  It  is 
found  in  many  American  localities,  especially,  Westmoreland,  X.  H.,  Blue  Hill  Bay, 
Maine,  Okanogan  Co. ,  Wash. ,  and  Pitkin,  Colorado.  Large  deposits  occur  at  Cooper, 
Maine,  and  are  now  being  mined. 

USES.  —  It  is  the  source  of  the  molybdenum  salts  which  are  im- 
portant chiefly  in  analytical  work.  Recently  quite  a  demand  has 
developed  for  molybdenum  for  toughening  and  hardening  steel,  it 
apparently  being  preferable  to  tungsten  for  this  purpose. 

MOLYBDITE. 

COMPOSITION. — MoO3,   (Mo  66.7  per  cent.). 

GENERAL  DESCRIPTION. — An  earthy  yellow  powder  or,  rarely,  tufts  and  hair-like 
crystals  of  yellowish  white  color. 

PHYSICAL  CHARACTERS. — Opaque  to  translucent.  Lustre,  dull  or  silky.  Color, 
yellow  or  yellowish  white.  Streak,  straw  yellow.  H.,  i  to  2.  Sp.  gr.,  4.49  to  4.5. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  fuses,  yielding  crystals  yellow  hot,  white 
cold,  and  made  deep  blue  by  the  reducing  flame.  In  borax  and  salt  of  phosphorus 
gives  characteristic  molybdenum  reactions. 

*  Best  seen  on  glazed  porcelain. 


CHAPTER   XXVIII. 


THE    COPPER   MINERALS. 


Cu    - 

Isometric 

Cu,S 
Cu,FeS4 
CuFeS,  - 

Orthorhombic 
Isometric 
Tetragonal 
Orthorhombic 

Cu*8sbS2s7 

Cu./) 
CuO 

Isometric 
Isometric 
Triclinic 

Cu(OH)Cl.Cu(OH)2 
CuS04.5H20 
Cu,(OH)C03 
Cus(OH)2(COs), 
CuSiO3.2H2O 

Orthorhombic 
Triclinic 
Monoclinic 
Monoclinic 

THE  minerals  described  are 
Metal  Copper 

Sulphides  Chalcocite 

Bornite 

Chalcopyrite 

Sulphoarsenite  Enargite 

Sulphoantimonite      Tetrahedrite 
Oxides  Cuprite 

Tenorite 

Basic  chloride  Atacamite 

Sulphates  Chalcanthite 

Carbonates  Malachite 

Azurite 
Silicates  Chrysocolla 

x»        Dioptase  H2CuSiO4  Hexagonal 

CTa-t~*4!e^£i.  C*4-»^S  -^2**  v»«<e' 'tf**r-«-ty  » 

In  addition  to  these  the  iron  sulphides  often  carry  copper  which 
is  extracted  after  burning  for  sulphuric  acid. 

The  chief  copper  minerals  are  chalcopyrite  and  bornite,  native 
copper,  cuprite,  malachite  and  azurite,  though  nearly  all  the  others 
above  mentioned  are  sufficiently  plentiful  to  be  considered  as  ores. 
The  world's  product*  of  copper  in  1902  was  533,763  metric  tons 
of  which  this  country  produced  277,047  tons.  In  1903  the  output 
of  the  United  States  had  increased  to  304,309  metric  tons,f  and 
of  the  total  product  of  the  world,  about  one-fourth  was  derived 
from  the  sulphide  ores  of  Montana,  and  one-sixth  from  the  native 
copper  of  Michigan.  Altogether,  the  United  States  yields  about 
two-thirds  of  the  copper  annually  produced. 

The  method  of  extraction  of  the  copper  is  dependent  upon  the 
nature  of  the  ore,  and  may  roughly  be  classed  under  three  head- 
ings : 

Treatment  of  native  copper. 

Treatment  of  oxidized  ores. 

Treatment  of  sulphides. 

*  <*(fineral  Industries,  1902,  p.  17^. 
f  Engineering  and  Mining  Journal,  1904,  p.  4. 
279 


^     J. 


280  DESCRIPTIVE  MINERALOGY. 

A  great  many  processes  exist  or  have  existed,  but  these  for  a 
general  brief  discussion  may  be  reduced  to  a  small  number  of  type 
processes  of  which  the  others  are  variations  due  to  local  conditions 
or  constituents  of  the  ore. 

Treatment  of  Native  Copper. 

Native  copper  occurs  in  enormous  quantities  in  Michigan,  and 
the  deposits  mined  average  less  than  two  per  cent,  of  copper,  al- 
though occasionally  large  masses  of  the  metal  are  found.  The 
rock  is  crushed  by  steam  stamps  and  the  copper  separated  from 
the  rock  by  the  action  of  water  and  the  use  of  jigs,  tables,  and  other 
concentrating  apparatus.  The  concentrated  material  is  then  melted 
in  a  large  reverberatory  furnace  with  limestone  and  slags  from  previ- 
ous operations.  The  new  slag  thus  formed  contains  the  remain- 
ing rock  and  is  removed,  leaving  behind  copper,  which  after  a 
period  of  reduction  by  charcoal  and  stirring  is  cast  into  ingots. 

Treatment  of  Oxidized  Ores. 

The  oxidized  ores  in  Arizona  which  average  over  ten  per  cent, 
of  copper,  are  smelted  in  blast-furnaces  with  coke  and  the  neces- 
sary flux  to  make  a  slag  with  the  associated  gangue.  The  result 
is  an  impure  metal  called  black  copper,  which  is  later  refined. 

Treatment  of  Sulphides. 

The  treatment  of  sulphides  is  quite  varied,  depending  chiefly  on 
the  presence  or  absence  of  arsenic,  the  richness  of  the  ore  and  the 
local  conditions.  The  ores  always  contain  iron,  copper  and  sul- 
phur, and  may  contain  arsenic,  antimony,  silver,  gold,  etc.  All 
the  smelting  processes  depend  on  the  facts  that  at  high  tempera- 
tures copper  has  a  greater  affinity  for  sulphur  than  iron  has,  and 
iron  a  stronger  affinity  than  copper  for  oxygen.  So  that  if  such 
an  ore  is  subjected  to  oxidation  by  roasting,  oxides  result ;  but  in 
the  subsequent  fusion,  if  enough  sulphur  has  been  left,  the  copper 
will  form  a  fusible  sulphide,  and  the  oxidized  iron  will  unite  with 
the  gangue  and  the  flux  to  form  a  slag. 

By  regulating  the  roasting,  the  sulphur  contents  may  be  brought 
to  any  desired  percentage.  This  may  be  just  sufficient  to  satisfy 
the  copper  or  to  satisfy  also  a  great  deal  of  the  iron  producing  a 
low-grade  sulphide  (matte),  which,  by  re-roasting  and  refusion,  is 
enriched.  The  low-grade  matte  means  a  smaller  loss  of  copper 


77/7:    COPPER   MINERALS. 
FIG.  389. 


28l 


Copper,  Calumet  and  Hecla  Mine,  Lake  Superior.     Columbia  University. 
FIG.  390. 


Copper,  Yadkin  Gold  Mine,  N.  C.     N.  Y.  State  Museum. 

in  the  slags,  and  is  often  of  service  in  assisting  the  removal  of  ar- 
senic and  antimony. 

When  the  matte  has  reached  the  required  percentage  of  copper, 
it  is  roasted  as  free  from  sulphur  as  possible,  and  being  now  essen- 


282 


DESCRIPTIVE  MINERAL  OG  Y. 


tially  an  oxide,  it  may  be  smelted  for  copper  either  in  a  shaft-fur- 
nace, much  as  the  oxidized  ores  are,  or,  when  silver  or  gold  is 
present,  in  a  reverberatory  furnace. 

In  a  more  recent  method  the  ores  are  roasted  and  fused,  pro- 
ducing a  matte  containing  over  fifty  per  cent,  of  copper.  This 
matte,  while  liquid,  is  run  into  a  sort  of  Bessemer  converter,  and 
a  blast  turned  on,  by  which  the  sulphur,  arsenic  and  antimony  are 
driven  off,  the  iron  oxidized  and  converted  into  slag,  and  black 
copper  obtained. 

The  crude  copper  is  refined  either  by  remelting  and  oxidation, 
or  more  frequently  electrolytically. 

The  great  uses  of  copper  are  in  electrical  work  and  in  alloys 
with  zinc  and  tin,  such  as  brass,  yellow  metal,  bronze,  bell  metal, 
German  silver,  etc.  In  1903  about  20,000  tons  of  copper  sulphate 
were  made  in  the  United  States. 


COPPER.  —  Native  Copper. 

COMPOSITION.  —  Cu   often  containing  Ag,  sometimes  Hg  or  Bi. 

GENERAL  DESCRIPTION. — A  soft,  red,  malleable  metal,  with  a 
red  streak.  Usually  in  sheets  or  disseminated  masses,  varying 
from  small  grains  to  several  hundred  tons  in  weight.  Also  in 
threads  and  wire  and  in  distorted  crystals  and  twisted  groups. 

CRYSTALLIZATION.  —  Isometric.  Tetrahexahedron  and  cube  most 
frequent,  Fig.  392,  also  twinned,  Fig.  393,  giving  by  elongation 
spear-shaped  forms  often  complexly  grouped  and  usually  distorted- 


FIG.  391. 


FIG.  392. 


FIG.  393. 


Physical  Characters.     H.,  2.5  to  3.     Sp.  gr.,  8.8  to  8.9. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  copper  red.  TENACITY,  malleable  and  ductile. 

COLOR,  copper  red,  tarnishing  nearly  black. 


THE   COPPER  MINERALS.  283 

BEFORE  BLOWPIPE,  ETC. — Fuses  easily  to  a  malleable  globule, 
often  coated  with  a  black  oxide.  In  beads,  becomes  in  O.  F.  green 
when  hot;  blue,  cold,  and  in  R.  F.  opaque  red.  Soluble  in  nitric 
acid,  with  evolution  of  a  brown  gas,  to  a  green  solution,  which  will 
deposit  copper  on  iron  or  steel.  The  solution  becomes  deep  azure 
blue  on  addition  of  ammonia. 

SIMILAR  SPECIES. — Resembles  niccolite  and  tarnished  siiver, 
differs  in  copper-red  streak. 

REMARKS. — Occurs  with  native  silver  and  ores  of  copper,  and  by  oxidation  may 
form  cuprite  or  melaconite  or  the  carbonates.  In  Michigan  it  occurs  in  trap  or 
conglomerate.  It  is  especially  apt  to  occur  near  dikes  of  igneous  rocks.  The 
great  locality  of  the  world  for  native  copper,  and  the  only  locality  still  yielding  this 
mineral  in  large  quantities,  is  the  Lake  Superior  region  of  Northern  Michigan,  and 
although  the  territory  here  covered  is  many  square  miles  in  extent,  the  Calumet  and 
Hecla  mine  yields  the  major  part  of  all  that  is  produced.  Although  native  copper  is 
also  found  in  Arizona,  California,  and,  to  a  limited  extent,  in  other  American  locali- 
ties, it  is  never  mined  for  itself  alone,  nor  does  it  constitute  a  large  part  of  the  copper 
ore  present.  The  Coro-Coro  mines,  in  Bolivia,  are  now  producing  some  copper  from 
the  native  metal. 

USES. — It  is  an  important  source  of  the  copper  of  commerce. 


CHALCOCITE.— Copper  Glance. 

COMPOSITION. — Cu2S,    (Cu  79.8,  S  20.2  per  cent.). 

GENERAL  DESCRIPTION. — Black  granular  or  compact  masses, 
vvith  metallic  lustre,  or  sometimes  nodules  or  pseudomorphic  after 
wood.  Often  coated  with  the  green  carbonate,  malachite.  Also 
in  crystals. 

CRYSTALLIZATION. — Orthorhombic,  d  :  b  :  t  =  0.582  :  i  :  0.970. 
J  A  /=  1 19°  35'.  O  A  i  =  1 17°  24^'.  Tabular  forms,  pseudo- 
hexagonal  or  frequently  twinned,  making  star-like  groups. 

Physical  Characters.     H.,  2.5  to  3.     Sp.  gr.,  5.5  to  5.8. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  lead  gray.-  TENACITY,  brittle. 

COLOR,  blackish  lead  gray,  with  dull-black  tarnish. 

BEFORE  BLOWPIPE,  ETC.— On  charcoal,  fuses  to  a  globule,  yield- 
ing sulphur  dioxide.  With  soda,  yields  a  copper  button  and  a 
strong  sulphur  reaction.  Colors  flame  emerald  green,  or  if  moist- 
ened with  hydrochloric  acid,  it  colors  the  flame  azure  blue.  In 
borax  or  salt  of  phosphorus,  yields  copper  beads.  Soluble  in  nitric 
acid,  leaving  a  residue  of  sulphur. 


284  DESCRIPTIVE  MINERALOGY. 

SIMILAR  SPECIES. — It  is  more  brittle  than  argentite,  and  differs 
from  bornite  in  not  becoming  magnetic  on  fusion. 

REMARKS. — Chalcocite  occurs  with  other  copper  minerals  and  with  hematite, 
galenite  and  cassiterite.  Is  found  at  Butte,  Montana,  and  other  American  localities  of 
less  importance.  Fine  crystals  are  obtained  from  Cornwall,  England. 

USES.  —  It  is  an  ore  of  copper. 

BORNITE.  —  Purple  Copper  Ore.     Horse  Flesh  Ore. 

COMPOSITION.  —  Cu5FeS4,  (Cu  63.3,  Fe  11.2,  S  25.5  per  cent), 
but  often  contains  admixed  chalcocite. 

GENERAL  DESCRIPTION. — On  fresh  fracture,  bornite  is  of  a  pecu- 
liar red-brown  color  and  metallic  lustre.  It  tarnishes  to  deep  blue 
and  purple  tints,  often  variegated.  Usually  massive,  sometimes 
small  cubes  or  other  isometric  forms. 

Physical  Characters.     H.,  3.     Sp.  gr.,  4.9  to  5.4. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  grayish  black.  TENACITY,  brittle. 

COLOR,  dark  copper  red,  brownish  or  violet  blue,  often  varied. 

BEFORE  BLOWPIPE,  ETC. — Blackens,  becomes  red  on  cooling, 
and  finally  fuses  to  a  brittle,  magnetic  globule  and  evolves  sulphur 
dioxide  fumes.  In  oxidizing  flame  with  borax  or  salt  of  phos- 
phorus, gives  green  bead  when  hot,  greenish  blue  when  cold,  the 
bead  is  opaque  red  in  the  reducing  flame.  Soluble  in  nitric  acid, 
with  separation  of  sulphur. 

REMARKS. — On  account  of  its  high  percentage  of  copper,  it  is  especially  valuable  as 
an  ore  of  copper  when  found  in  quantity.  A  large  portion  of  the  ore  of  many  of  the 
Chilian  mines  consists  of  bornite,  and  it  has  been  found  in  quantity  in  the  Montana 
copper  regions.  Also  found  at  Bristol,  Conn. ;  Acton,  Canada :  in  Mexico,  in  Peru 
and  other  copper  regions. 

USES. — It  is  an  important  ore  of  copper. 

CHALCOPYRITE.— Copper  Pyrites.     Yellow  Copper  Ore. 

COMPOSITION.— CuFeS2,  (Cu  34.5,  Fe  30.5,  S  35.0 per  cent),  with 
mechanically  intermixed  pyrite  at  times. 

GENERAL  DESCRIPTION. — A  bright  brassy  yellow  mineral  of 
metallic  lustre,  often  with  iridescent  tarnish  resembling  that  of 
bornite.  Usually  massive.  Sometimes  in  crystals. 

CRYSTALLIZATION. — Tetragonal.  Scalenohedral  class,  p.  41. 
Axis  c=  0.985. 

Sphenoids    predominate,  /  =  unit    sphenoid  ;  o  =  (a  :  a  :  ^c)  ; 


THE  COPPER  MINERALS. 


285 


{772};  t=(a:a:{c);  { 1 14}  ;  v  =  (a  :  a  :  4r)  ;  {441};  *  = 
(a\2a\c)\  {212}. 

Supplement  angles  (over  top)  // =  108°  40'  ;  00=  128°  52'  ; 
tt=  38°  25';  w=  159°  39'. 


FIG.  394. 


FIG.  395. 


FIG.  396. 


French  Creek,  Pa. 


Ellenville,  N.  Y. 


Physical  Characters.     H.,  3.5  to  4.     Sp.  gr.,  4.1  to  4.3. 

LUSTRE,  metallic.  OPAQUE. 

STREAK,  greenish  black.  TENACITY,  brittle. 

COLOR,  bright  brass  yellow,  often  tarnished  in  blue,  purple  and 
black  hues. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  fuses  with  scintillation  to 
a  brittle  magnetic  globule.  With  soda  yields  metallic  malleable 
red  button  and  sulphur  test.  In  closed  tube  decrepitates,  becomes 
dark  and  iridescent  and  may  give  deposit  of  sulphur.  Flame  and 
bead  reaction  like  bornite.  Soluble  in  nitric  acid  with  separation 
of  sulphur,  and  from  the  solution  ammonia  throws  down  a  brown 
precipitate,  and  leaves  the  liquid  deep  blue  in  color. 

SIMILAR  SPECIES. — Chalcopyrite  is  softer  and  darker  in  color 
than  pyrite,  and  differs  from  gold  in  black  streak  and  brittleness. 

REMARKS. — Chalcopyrite  is  probably  formed  in  a  manner  similar  to  the  formation 
of  pyrite  which  is  its  frequent  associate.  Its  most  prominent  associated  minerals  are 
the  metallic  sulphides  and  copper  ores,  many  of  which  have  been  formed  by  its 
alteration.  It  sometimes  contains  gold  or  silver.  It  is  a  very  widely  distributed  mineral 
and  the  major  part  of  all  the  copper  produced  is  made  from  it.  Prominent  mines  are 
in  the  Butte,  Montana,  region  ;  and  in  Bingham  Canyon,  Utah.  Also  produced  in 
large  quantities,  at  Falun  in  Sweden  ;  Rio  Tinto,  Spain  ;  Sudbury,  Canada  ;  and  many 
other  important  localities. 


USES.  —  It  is  the  great  ore  of  copper. 


286 


DESCRIPTIVE  MINERALOGY. 


FIG.  397. 


ENARGITE. 

COMPOSITION.  —  Cu3AsS4,  (Cu  48.3,  As  19.1,  S  32.6  per  cent.). 
Sometimes  with  Cu  replaced  in  part  by  Zn  or  Fe  and  As  by  Sb. 
GENERAL  DESCRIPTION. —  A  black  brittle  min- 
eral of  metallic  lustre,  occurring  usually  colum- 
nar or   granular  but   sometimes   in    orthorhom- 
bic  crystals. 

CRYSTALLIZATION.  —  Orthorhombic.    Axes  a  : 
b  :  c  =  0.871  :  i  :  0.825.      ;//  —  un^  prism,   /  = 
(2^:£:co<r);    (120).     Supplement   angles   are 
mm=  82°  7';  //=  120°  7' . 
Missouia  Co.,  Mont.    Physical  Characters.     H.,  3.     Sp.  gr.,  4.43  to 

4.45. 

LUSTRE,  metallic.  OPAQUE. 

STREAK,  blackish  gray.  TENACITY,  brittle. 

COLOR,  black  or  blackish  gray. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  fuses,  yields  white  fumes 
with  garlic  odor.  With  soda  yields  malleable  copper  and  a  reaction 
for  sulphur.  In  closed  tube  decrepitates,  yields  sulphur  sublimate, 
then  fuses  and  yields  red  sublimate  of  arsenic  sulphide.  Soluble 
in  nitric  acid. 

REMARKS. — Enargite  occurs  with  other  copper  minerals,  especially  arsenates  derived 
from  its  alteration.  It  is  found  mainly  in  the  mountains  of  Chili  and  Peru.  Also  at 
Butte,  Montana,  Gilpin  county,  Colorado ;  in  South  Carolina,  Utah  and  California. 

USES. — It  is  an  ore  of  copper,  and  has  been  extensively  mined. 

TETRAHEDRITE.  —  Gray  Copper  Ore. 

COMPOSITION.  —  Cu8Sb.2S7.  Cu  often  partially  replaced  by  Fe, 
Zn,  Pb,  Hg,  Ag,  and  the  Sb  by  As. 

GENERAL  DESCRIPTION.  —  A  fine  grained,  dark  gray  mineral  of 


FIG.  398. 


FIG.  399. 


FIG.  400. 


THE    COPPER  MINERALS.  287 

metallic  lustre.      Characterized  especially  by  the  tetrahedral  habit 
of  its  crystals  which  are  sometimes  coated  with  yellow  chalcopyrite. 

FIG-  401.  FIG.  402. 


CRYSTALLIZATION.  —  Isometric.  Hextetrahedral  class,  p.  56. 
The  tetrahedron  /,  Fig.  398,  usually  predominates,  often  modified 
by  the  tristetrahedron  n  =  (a  :  2a  :  20) ;  {211};  Figs.  401,  402, 
403,  and  less  frequently  by  other  forms  such  as  the  dodecahedron 
d,  Figs.  399  and  403,  and  the  deltohedron  r  =  (a  :  a  :  20)  ;  {221}; 
Fig.  400. 

Physical  Characters.     H.,  3  to  4.5.     Sp.  gr.,  4.5  to  5.1. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  black  or  reddish  brown.  TENACITY,  brittle. 

COLOR,  light  steel  to  dark  lead  gray  or  iron  black. 

BEFORE  BLOWPIPE,  ETC.— On  charcoal  fuses  easily  to  a  globule 
which  may  be  slightly  magnetic.  Evolves  heavy  white  fumes 
with  sometimes  garlic  odor.  The  roasted  residue  gives  bead  and 
flame  reactions  for  copper.  Soluble  in  nitric  acid  to  a  green  solu- 
tion with  white  residue. 

VARIETIES — Varieties  based  upon  the  replacing  metal  as  mercuric, 
argentiferous,  platiniferous,  bismuthiferous,  etc.,  are  given  special 
names  as  Freibergite,  Schwatzite,  Rionite,  etc. 

SIMILAR  SPECIES. — The  crystals  are  characteristic.  The  fine 
grained  fracture  in  conjunction  with  the  color  is  often  sufficient  to 
distinguish  it.  It  is  softer  than  arsenopyrite  and  the  metallic  cobalt 
ores,  and  does  not  generally  yield  a  strongly  magnetic  residue  on 
heating.  Bournonite  and  chalcocite  are  softer,  and  finally  the 
blowpipe  reactions  are  distinctive. 

REMARKS. -Occurs  with  the  sulphides  of  lead,  silver,  copper,  etc.,  especially  in 
Humbolt  County,  Nevada,  and  numerous  localities  in  Colorado.  Also  in  Mexico, 
Bolivia,  Chili,  and  in  many  parts  of  Europe. 

USES. — It  is  sometimes  worked  for  silver  and  also  for  copper. 


DESCRIPTIVE  MINERALOGY. 


Tennanite.  —  Cu8As2S7.  This  mineral  grades  into  tetrahedrite  and  is  undistinguish- 
able  by  crystal  form  or  general  appearance.  It  occurs  in  crystals  and  is  said  to  occur 
massive  in  Utah  with  enargite. 

CUPRITE. —  Red  Oxide  of  Copper,  Ruby  Copper  Ore. 

COMPOSITION.  —  Cu2O  (Cu  88.8  per  cent).  Sometimes  inter- 
mixed with  limonite. 

GENERAL  DESCRIPTION. —  Fine  grained  masses,  dark  red,  brown- 
ish-red and  earthy  brick-red  in  color ;  or  deep  red  to  crimson, 
transparent,  isometric  crystals,  usually  octahedrons,  or  cubes. 
Also  capillary. 

FIG.  403.  FIG.  404.  FIG.  405. 


CRYSTALLIZATION.  —  Isometric.      Class  of  gyroid,  p.  60.     The 
octahedron  /,  cube  a  and  dodecahedron  d  predominating.      Index 
of  refraction  for  red  light  2.849. 
Physical  Characters.     H.,  3.5  to  4.     Sp.  gr.,  5.85  to  6.15. 

LUSTRE,  adamantine  or  dull.  TRANSPARENT  to  opaque. 

STREAK,  brownish  red.  TENACITY,  brittle. 

COLOR,  crimson,  scarlet,  vermilion,  or  brownish  red. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  blackens  and  fuses  easily 
to  a  malleable  red  button.  Flame  and  bead  tests  give  the  color  for 
copper.  Soluble  in  nitric  acid  to  a  green  solution.  Soluble  also 
in  strong  hydrochloric  acid  to  a  brown  solution  which  diluted  with 
water  yields  a  white  precipitate. 

SIMILAR  SPECIES. — It  is  softer  than  hematite  and  harder  than 
cinnabar  or  proustite,  and  differs  from  them  all  by  yielding  an 
emerald-green  flame  and  a  malleable  red  metal  on  heating. 

REMARKS. — It  is  formed  by  oxidation  of  sulphides  or  the  metal,  and  is  found  near  the 
surface  associated  with  limonite,  quartz,  and  copper  minerals.  It  changes  to  the  Black 
oxide  and  to  the  carbonates  and  silicate.  In  the  United  States  it  is  especially  abundant 
in  the  Arizona  copper  region.  Also  found  in  the  Lake  Superior  region,  and  is  abun- 
dant in  Chili,  Peru  and  Bolivia  in  association  with  the  other  copper  ores. 

USES. — It  is  an  important  ore  of  copper. 


THE    COPPER   MINERALS.  289 

TENORITE.— Melaconite,  Black  Oxide  of  Copper. 

COMPOSITION. — CuO,    (Cu  79.85  per  cent.). 

GENERAL  DESCRIPTION. — Dull  black  earthy  masses,  black  powder  and  shining 
black  scales. 

PHYSICAL  CHARACTERS.— Lustre,  metallic  in  scales,  dull  in  masses.  Color  and 
streak  black.  H.,  3.  •  Sp.  gr.,  5.82  to  6.25. 

BEFORE  BLOWPIPE,  ETC. — Infusible,  otherwise  like  cuprite. 

REMARKS.— Occurs  in  fissures  in  the  lava  of  Vesuvius,  as  a  black  coat  on  chalcopy- 
rite  and  as  dull  black  masses  with  chrysocolla. 

ATACAMITE. 

COMPOSITION.— Cu(OH)Cl-Cu(OH)2,    (Cu  59.45,  Cl  16.64  per  cent.). 

GENERAL  DESCRIPTION.— Confused  aggregates  of  crystals  of  bright  or  dark-green 
color.  Also  granular  or  compact  massive,  or  as  a  crust.  Rarely  in  slender  orthorhom- 
bic  prisms. 

PHYSICAL  CHARACTERS. — Translucent  to  transparent.  Lustre,  adamantine  to  vit- 
reous. Color,  bright  green,  emerald  green,  blackish  green.  Streak,  apple  green. 
H.,  3103.5-  Sp.gr.,  3-75  to  3-77- 

BEFORE  BLOWPIPE,  ETC.  —  On  charcoal  yields  white  fumes  and  a  coating  which  is 
brown  near  the  assay  and  white  at  some  distance  from  it,  fuses  to  a  copper-red,  malle- 
able button,  and  colors  the  flame  a  beautiful  and  persistent  blue  without  the  aid  of 
hydrochloric  acid.  In  closed  tube  yields  water  and  a  gray  sublimate.  Soluble  in  acids 
to  a  green  solution. 

CHALCANTHITE.— Blue  Vitriol. 

COMPOSITION.— CuSO4-5H2O,    (CuO  31.8,  SOS  32.1,  H2O  36.1  per  cent). 

GENERAL  DESCRIPTION. — A  blue,  glassy  mineral,  with  a  disagreeable  metallic  taste. 
It  occurs  usually  as  an  incrustation,  with  fibrous,  stalactitic  or  botryoidal  structure;  but 
sometimes  in  flat  triclinic  crystals. 

PHYSICAL  CHARACTERS.— Translucent.  Lustre,  vitreous.  Color,  deep  blue  to 
sky  blue.  Streak,  white.  H.,  2.5.  Sp.  gr,  2.12  to  2.30.  Brittle.  Taste,  metallic 
nauseous. 

CRYSTALLIZATION. — Triclinic.       Axes  a  :b~.  ^  =  0.566  :  pIG 

I  :  0.551.  Axial  angles  0  =  82°  2l';  ,3  =  73°  il';  7  =  77° 
37'.  Prominent  forms,  right  and  left  unit  prisms  m  and  M, 
unit  pyramid  p,  and  the  pinacoids  a  and  b.  Angles  mM= 
56°  50'.  Optically—. 

BEFORE  BLOWPIPE,  ETC.  —  On  charcoal,  fuses,  coloring 
flame  green  and  leaving  metallic  copper.  In  closed  tube 
yields  water  and  sulphur  dioxide  and  leaves  a  white  powder. 
Easily  soluble  in  water  to  a  blue  solution. 

REMARKS.  —It  is  produced  by  oxidation  of  the  sulphides, 
especially  chalcopyrite.  Copper  is  sometimes  precipitated  from 
mine  waters  containing  chalcanthite. 


Brochantite.  —  CuSO4  3Cu(OH)2.     Velvety,    emerald-green  crusts  of   fine  needle 
crystals  and  botryoidal  masses. 

Liebethenite. — Cu2(OH)PO4.     Dark,   olive-green    mineral,   usually    in   druses   of 
short  prismatic  orthorhombic  crystals,  more  rarely  compact. 

'9 


290  DESCRIPTIVE  MINERALOGY. 

Olivenite.  —  Cu.j(OH)AsO4.     Needle-like  orthorhombic  crystals  of  dark  olive-green, 
also  nodules  and  fibrous  or  velvety  masses  of  light-green  to  gray  or  brown  color. 


MALACHITE.— Green  Carbonate  of  Copper. 

COMPOSITION.— Cu,(OH)2CO3,  (CuO  71.9,  CO,  19.9,  H2O  8.2 
per  cent.) 

GENERAL  DESCRIPTION. — Bright-green  masses  and  crusts,  often 
with  a  delicate,  silky  fibrous  structure  or  banded  in  lighter  and 
darker  shades  of  green.  Sometimes  stalactitic.  Also  in  dull- 
green,  earthy  masses,  and  rarely  in  small,  slender,  monoclinic 
crystals.  Frequently  coating  other  copper  minerals  or  filling 
their  crevices  and  seams. 

Physical  Characters.     H.,  3.5  to  4.     Sp.  gr.,  3.9  to  4.03. 
LUSTRE,  silky,  adamantine  or  dull.    TRANSLUCENT  to  opaque. 
Streak,  pale  green.  TENACITY,  brittle. 

COLOR,  bright  emerald  to  grass  green  or  nearly  black. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal,  decrepitates,  blackens, 
fuses,  and  colors  the  flame  green,  leaving  a  globule  of  metallic 
copper.  In  closed  tube,  blackens  and  yields  water  and  carbon 
dioxide.  Soluble  in  acids,  with  effervescence. 

SIMILAR  SPECIES. — Distinguished  by  color  and  effervescence 
with  acids. 

REMARKS. — Malachite  is  formed  by  action  of  carbonated  waters  on  other  copper 
minerals.  It  is  found  chiefly  with  these  or  pseudomorphous  after  them,  especially 
after  cuprite  and  azurite.  Immense  deposits  occur  at  Bisbee,  Arizona,  and  other  local- 
ities in  the  same  region.  Also  in  large  deposits  in  Siberia,  Chili  and  Australia.  In 
smaller  quantities  it  is  found  in  the  vicinity  of  all  copper  ores. 

USES. — Is  an  ore  of  copper,  and  like  marble  is  polished  for  or- 
namental articles,  table- tops,  etc. 

AZURITE. — Blue  Carbonate  of  Copper. 

COMPOSITION.  —  Cu3(OH)2(CO3)2,  (CuO  69.2,  CO2  25.6,  H2O  5.2 
per  cent.). 

GENERAL  DESCRIPTION.  —  A  dark -blue  mineral  occurring  in 
highly  modified,  glassy,  monoclinic  crystals  and  groups.  When 
massive,  it  may  be  vitreous,  velvety,  or  dull  and  earthy.  It  fre- 
quently occurs  incrusting  other  copper  ores,  or  distributed  through 
their  cracks  and  crevices. 


THE    COPPER   MINERALS.  2gi 

CRYSTALLIZATION.  —  Monoclinic.     Axes  a  :  ~b  :  c  =  0.850  :  i  : 
0.88i  ;  ^=87°  36'. 

Crystals  very  varied  in  habit.     Those  figured  show  basal  pina- 

FIG.  407.  FIG.  408. 


Arizona.  Chessy,  France. 

coid  c,  ortho-pinacoid  a,  unit  prism  ;;/,  unit  dome  o,  and  the  pyra- 
mids /,  r,  and  v.  Supplement  angles  are  mm  =  80°  41';  co  =  44° 
46'.  Optically  +. 

Physical  Characters.     H.,  3.5  to  4.     Sp.  gr.,  3.77  to  3.83. 
LUSTRE,  vitreous.  TRANSLUCENT  to  opaque. 

STREAK,  blue.  TENACITY,  brittle. 

COLOR,  dark  blue  to  azure  blue. 

BEFORE  BLOWPIPE,  ETC. — As  for  malachite. 

REMARKS. — Origin,  associates  and  localities  are  the  same  as  for  malachite. 

USES. — As  an  ore  of  copper  and  a  rather  unsatisfactory  blue 
paint. 

CHRYSOCOLLA. 

COMPOSITION. — CuSiO3  +  2H2O.  Often  very  impure  (CuO  45.2, 
SiO2  34.3,  H2O  20.5  per  cent.). 

GENERAL  DESCRIPTION. — Green  to  blue  incrustations  and  seams 
often  opal-like  in  texture,  or  sometimes,  from  impurities,  resem- 
bling a  kaolin  colored  by  copper.  Also  brown,  resembling  limonite, 
and  in  dull  green  earthy  masses.  Never  found  in  crystals. 

Physical  Characters.     H.,  2  to  4.     Sp.  gr.,  2  to  2.3. 

LUSTRE,  vitreous,  dull.  TRANSLUCENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  green  to  light  blue,  brown  when  ferriferous. 

BEFORE  BLOWPIPE.  ETC. — In  forceps  or  on  charcoal  is  infusible, 
but  turns  black,  then  brown  and  colors  the  flame  emerald  green.  In 


292 


DESCRIPTIVE  MINERALOGY. 


bead,  reacts  for  copper.  With  soda,  yields  malleable  copper.  In 
closed  tube,  yields  water.  Decomposed  by  hydrochloric  acid, 
leaving  a  residue  of  silica.  Boiled  with  KOH,  yields  a  blue  solu- 
tion, from  which  excess  of  NH4C1  precipitates  flocculent  H2SiO3. 

SIMILAR  SPECIES. — It  is  softer  than  turquois  or  opal  and  does  not 
effervesce  like  malachite. 

REMARKS. — Chrysocolla  occurs  with  other  copper  minerals,  especially  near  the  tops 
of  veins.  It  is  probably  formed  by  the  action  of  hot  solutions  of  alkaline  silicates 
on  other  copper  ores.  Found  at  Clifton,  Arizona ;  Hartville,  Wyoming,  and  in  most 
of  the  prominent  copper-bearing  regions. 

USES. — As  an  ore  of  copper  and  an  imitation  turquois. 

DIOPTASE. 

COMPOSITION.— H2CuSiO<,    (CuO  50.4,  SiO2  38.2,  H2O  11.4  per  cent.). 


FIG.  409. 


GENERAL  DESCRIPTION. — Glassy,  emerald-green  crystals  and 
druses  of  indistinct  crystals.  Also  found  massive. 

CRYSTALLIZATION. — Hexagonal,  c  =  0.534.  J?  A  Jl  =  125° 
55'.  2  A  2  —  95°  26%'.  Commonly  prismatic,  with  rhombo- 
hedral  terminations. 

PHYSICAL  CHARACTERS.  Transparent  to  opaque.  Lustre, 
vitreous  Color,  emerald  green.  Streak,  green.  H ,  5.  Sp. 
gr.,  3.28  to  3.35.  Brittle.  Cleavage,  rhombohedral. 

BEFORE  BLOWPIPE,  ETC. — Decrepitates,  blackens,  colors  the 
flame  emerald  green,  but  is  infusible.  In  closed  tube,  blackens 
and  yields  water.  Gelatinizes  with  acids. 


CHAPTER   XXIX. 

MERCURY   AND    SILVER    MINERALS. 
THE    MERCURY    MINERALS. 

THE  minerals  described  are  : 

Metal  Mercury  Hg 

Sulphide  Cinnabar  HgS  Hexagonal 

Chloride  Calomel  Hg2Cl,,  Tetragonal 

The  only  ore  is  cinnabar,  with  which  the  native  metal  sometimes 
occurs  in  small  quantities.  The  ore  is  usually  low  grade,  that 
mined  in  this  country  yielding  an  average  of  less  than  one  per  cent, 
of  mercury.  The  world's  product  of  mercury  in  1902  was  about 
3,000  metric  tons,  of  which  the  United  States  produced  one-third. 
In  1903  the  output  of  the  United  States  was  1,010  metric  tons.* 

Mercury  is  obtained  from  cinnabar  by  heating  the  larger  lumps 
in  a  shaft-furnace,  resembling  a  continuous  lime  kiln,  with  three 
exterior  fire  places.  A  little  fuel  is  also  mixed  with  the  ore.  The 
heat  decomposes  the  sulphide,  forming  fumes  of  sulphur  dioxide 
and  mercury.  These  fumes  are  carried  off  through  large  iron 
pipes  to  condensers  where  the  mercury  is  liquified.  The  finer  ore  is 
heated  in  a  vertical  shaft  containing  a  series  of  inclined  shelves  down 
which  the  ore  slips  whenever  any  is  drawn  off  at  the  bottom.  The 
fumes  go  to  the  condensers  already  mentioned. 

Mercury  is  extensively  used  in  certain  processes  for  the  extrac- 
tion of  gold  and  silver  from  their  ores  and  in  the  manufacture  of 
vermilion.  Minor  uses  are  in  barometers,  thermometers,  silvering 
mirrors,  and  in  medicine. 

MERCURY. 

COMPOSITION'. — Hg,  with  sometimes  a  little  silver. 

GENERAL  DESCRIPTION. — A  tin  white  liquid  with  metallic  lustre.  Usually  found  in 
little  globules  scattered  in  the  gangue,  or  in  cavities  with  cinnabar  or  calomel. 

PHYSICAL  CHARACTERS. — Opaque  liquid.     Lustre,  metallic.    Color,  tin  white.     Sp. 

gr->  I3-59- 

BEFORE  BLOWPIPE,  ETC. — Entirely  volatile.  In  matrass  or  closed  tube  may  be 
collected  in  small  globules.  Soluble  in  nitric  acid. 

*  Engineering  and  Mining  Journal,  1904,  p.  4. 
293 


294  DESCRIPTIVE  MINERALOGY. 

CINNABAR.— Natural  Vermilion. 

COMPOSITION. — HgS,    (Hg  86.2  per  cent.). 

GENERAL  DESCRIPTION. — Very  heavy,  bright  vermilion  to  brown- 
ish  red  masses  of  granular  texture ;  more  rarely  small  transparent 
rhombohedral  crystals,  or  bright  scarlet  powder,  or  earthy  red  mass. 
Sometimes  nearly  black  from  organic  matter. 
Physical  Characters.     H.,  2  to  2.5.     Sp.  gr.,  8  to  8.2. 

LUSTRE,  adamantine  to  dull.  OPAQUE  to  transparent. 

STREAK,  scarlet.  TENACITY,  brittle  to  sectile. 

COLOR,  cochineal  red,  scarlet,  reddish  brown,  blackish. 

BEFORE  BLOWPIPE,  ETC.  —  Completely  volatilized  without  fusion 
if  pure.  With  soda  gives  sulphur  reaction.  In  closed  tube  yields 
a  black  sublimate,  which  becomes  red  when  rubbed  ;  if  soda  is  used 
a  metallic  mirror  is  obtained  instead  of  the  black  sublimate,  and  by 
rubbing  with  a  splinter  of  wood  globules  of  mercuiy  may  be  col- 
lected. If  cinnabar  powder  is  moistened  with  hydrochloric  acid  and 
rubbed  on  bright  copper  the  copper  is  made  silver  white.  Soluble 
in  aqua  regia. 

SIMILAR  SPECIES.  —  Cinnabar  is  softer  and  heavier  than  hematite, 
cuprite,  and  rutile.  It  has  a  more  decided  red  streak  than  crocoite 
or*  realgar,  and  differs  from  proustite  in  density  and  blowpipe 
reactions. 

REMARKS.  —  Cinnabar  occurs  in  slates  and  shales,  and  sometimes  in  granite  or 
porphyry  associated  with  sulphides  of  iron,  copper,  antimony,  and  arsenic,  and  with 
native  gold.  Its  chief  localities  are  Idria,  southern  Austria  ;  Almaden,  Spain  ;  Huan- 
cavelica,  Peru  ;  Kwei-chan,  China  ;  Ekaterinoslav,  Russia,  and  at  several  places  in 
Lake,  San  Benito,  Napa,  and  Santa  Clara  counties,  California.  Cinnabar  is  also 
mined  at  Terlingua,  Texas,  and  Bald-Butte,  Oregon.  The  United  States  is  now  the 
largest  producer. 

USES. — It  is  the  only  important  ore  of  mercury.  The  artificial 
cinnabar  is  the  important  pigment  vermilion. 

CALOMEL  -Horn  Mercury. 

COMPOSITION. — Hg2Cl2)    (Hg  84.9  per  cent.). 

GENERAL  DESCRIPTION. — A  gray  or  brown  translucent  mineral  of  the  consistency 
of  horn.  Usually  found  as  a  coating  in  cavities  with  or  near  cinnabar.  Sometimes 
in  well-developed  tetragonal  forms  c  —  1.723. 

PHYSICAL  CHARACTERS.— Translucent.  Lustre,  adamantine.  Color,  gray,  white, 
brown.  Streak,  white.  H.,  I  to  2.  Sp.  gr.,  6.48.  Very  sectile. 

BEFORE  BLOWPIPE,  ETC.— Volatilizes  without  fusion,  yielding  a  white  coating.  In 
closed  tube  with  soda  forms  a  metallic  mirror. 


MERCURY  AND   SILVER  MINERALS. 


295 


THE    SILVER    MINERALS. 

The  minerals  described  are  : 

Metal 

Silver 

Ag 

Sulphides 

Amalgam 
Argentite 

Ag2Hg3  to  Ags6Hg 
Ag2S 

Stromeyerite 

CuAgS 

Telluride 

Hessite 

Ag2.Te 

Sulphoarsenite 

Proustite 

Ag3AsS3 

Sulphoantimonites 

Pyrargyrite 

Ag3SbS3 

Stephanite 

Ag5SbS, 

Polybasite 

(Ag.Cu)9SbS, 

Halides 

Cerargyrite 

AgCl 

Bromyrite 

AgBr 

Embolite 

Ag(Br.Cl) 

lodyrite 

Agl 

Isometric 

Isometric 

Isometric 

Orthorhombic 

Isometric 

Hexagonal 

Hexagonal 

Orthorhombic 

Orthorhombic 

Isometric 

Isometric 

Isometric 

Hexagonal 

Ordinary  silver  ores  contain  less  than  one  per  cent,  of  the  silver 
compounds  distributed  through  various  earthy  and  metallic  min- 
erals, and  only  show  the  true  nature  of  the  silver-bearing  sub- 
stance in  occasional  rich  specimens.  Frequently  an  ore  will  con- 
tain less  than  twenty  ounces  of  silver  per  ton. 

In  1902*  the  production  of  silver  was  55,500,000  ounces  in 
this  country  alone,  and  the  product  of  the  world  was  163,936,- 
704  ounces.  In  1903  the  United  States  produced  56,519,000 
ounces,  valued  at  $30,520,688.1 

The  extraction  of  silver  by  reduction  with  lead-ores  in  a  water- 
jacket  furnace,  and  the  subsequent  treatment  has  been  referred  to 
under  lead,  p.  256.  When  silver  is  a  constituent  of  a  copper 
matte  it  is  recovered  as  a  sedimentary  product  in  the  electrolytic 
refining  of  the  copper.  It  is  collected,  together  with  any  gold 
present,  and  further  purified. 

In  some  instances  the  silver  is  extracted  from  the  pre  by  wet 
processes  or  by  treatment  with  mercury. 

Several  processes  for  extracting  silver  by  the  use  of  mercury 
exist,  the  principle  in  every  case  being  that  mercury  will  reduce 
certain  compounds  of  silver  to  metal  and  unite  with  the  silver,  or 
if  mercury  is  present  and  some  other  substance,  as  iron  or  copper, 
reduces  the  ore  to  silver,  the  mercury  will  collect  it. 

The  details  of  amalgamation  are  in  transforming  the  silver  to  a 
condition  in  which  the  mercury  can  act  —  for  instance,  forming 
chlorides  by  roasting  with  salt  —  and  in  the  method  of  reduction. 

.  *  Mineral  Industry,  1902,  254. 
f  Engineering  and  Mining  Journal,  1904,  p.  5. 


296 


DESCRIPTIVE  MINERALOGY. 


In  pan  amalgamation,  so  called,  the  finely-crushed  ore,  chlorid- 
ized  when  necessary,  and  mixed  to  a  pulp  with  water,  is  charged 
into  a  tub-like  vessel,  with  an  iron  bottom  and  wooden  sides.  In 
this  tub  or  pan  there  revolves  a  stirrer,  with  arms  shaped  to 
throw  the  pulp  to  the  sides,  from  which  it  rolls  back  to  the 
centre.  Attached  to  the  arms  are  grinding  shoes,  which  can  be 
lowered  so  as  to  rub  on  the  iron  bottom  or  be  raised  free  from  it. 
The  practice  will  differ  in  detail,  but  generally  the  pulp  will  be 
kept  hot  by  steam,  and  no  mercury  will  be  added  until  the  grind- 
ing is  completed.  During  the  grinding  the  metallic  iron  of  the 
bottom  and  the  shoes  reduces  the  silver  compound ;  although 
chemicals,  such  as  salt,  copper  sulphate,  potassium  cyanide,  etc., 
are  sometimes  added  to  assist.  After  the  grinding  the  mercury  is 
added,  and  the  stirring  continued  until  the  mercury  has  collected 
all  the  silver.  The  mass  is  then  run  into  a  larger  tub,  diluted,  the 
mercury  amalgam  separated,  and,  by  subsequent  distillation,  the 
silver  recovered  from  the  mercury. 

SILVER.— Native  Silver. 

COMPOSITION. — Ag,  sometimes  alloyed  with  Au,  Cu,  Pt,  Hg, 
Sb,  Bi. 

FIG.  410. 


Wire  Silver.     After  Lacroix. 


GENERAL  DESCRIPTION. — A  silver-white,  malleable  metal,  oc- 
curring in  masses,  scales  and  twisted  wire-like  filaments,  Fig.  410, 


MERCURY  AND   SILVER   MINERALS.  297 

penetrating  the  gangue  or  flattened  upon  its  surface.  Sometimes 
in  isometric  crystals,  occasionally  sharp  but  more  frequently 
elongated  and  needle-like  or  in  aborescent  groups,  each  branch  of 
which  is  composed  of  distorted  forms  in  parallel  position. 

Physical  Characters.     H.,  2.5  to  3.     Sp.  gr.,  10.1  to  n.i. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  silver  white.  TENACITY,  malleable. 

COLOR,  silver  white,  tarnishing  brown  to  nearly  black. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal,  fuses  to  a  white  metallic 
globule.  Soluble  in  nitric  or  sulphuric  acid,  but  from  these  it  is 
precipitated  as  a  white  curd-like  precipitate  by  hydrochloric  acid  or 
salt.  The  precipitate  darkens  on  exposure  to  light. 

SIMILAR  SPECIES.  —  When  tarnished,  silver  resembles  copper  or 
bismuth,  but  is  distinguished  by  its  silver-white  streak  from  the 
former  and  by  malleability  and  non-volatilization  from  the  latter. 

REMARKS. — Silver  may  have  been  formed  by  the  reduction  of  its  ores,  as  it  occurs 
pseudomorphous  after  them.  It  is  also  changed  to  sulphides  by  contact  with  soluble 
sulphides,  and  into  the  chloride  by  salt  water.  Its  associates  are  the  other  silver 
minerals,  and  galenite,  pyrite,  stibnite,  tetrahedrite,  etc. 

The  most  celebrated  mines  where  native  silver  is  obtained  are  those  of  Kongsberg, 
in  Norway,  and  Huantaya,  Peru.  Occurs  also  in  Northern  Mexico,  in  the  Michigan 
copper  region,  in  numerous  Colorado  localities,  at  Butte,  Montana  ;  in  Idaho ;  Arizona, 
and  in  smaller  quantity  in  other  silver-producing  regions. 

AMALGAM. 

COMPOSITION.— Ag2Hg,  to  Ag^Hg. 

GENERAL  DESCRIPTION. — A  brittle,  silver- white  mineral  of  bright  metallic  lustre, 
which  occurs  in  imbedded  grains  and  indistinct  isometric  crystals. 

PHYSICAL  CHARACTERS. — Opaque,  lustre  metallic.  Color  and  streak,  silver  white. 
H.,  3  to  3.5.  Sp.  gr.,  13.75  to  14.1.  Somewhat  brittle  and  cuts  with  a  peculiar 
grating  noise. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal,  partially  volatilized,  leaving  malleable  silver. 
In  closed  tube,  yields  mercury  mirror.  Soluble  in  nitric  acid. 

ARGENTITE.  —  Silver  Glance. 

COMPOSITION.  —  Ag2S,  (Ag  87.  i  per  cent.). 

GENERAL  DESCRIPTION.  —  A  soft  black  mineral,  of  metallic  lustre, 
which  cuts  like  wax  and  occurs  as  masses,  disseminated  grains,  or 
incrusting.  Also  found  as  isometric  crystals,  the  cube,  octahe- 
dron, or  dodecahedron  being  most  common  and  frequently  grouped 
in  parallel  positions. 


298  DESCRIPTIVE  MINERALOGY. 

Physical  Characters.  —  H.,  2  to  2.5.     Sp.  gr.,  7.2  to  7.36. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  lead  gray.  TENACITY,  very  sectile. 

COLOR,  lead  gray  to  black  or  blackish  gray. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal,  swells,  fuses,  yields 
fumes  of  sulphur  dioxide,  and  finally  malleable  silver.  Soluble 
in  nitric  acid,  with  separation  of  sulphur. 

SIMILAR  SPECIES. — Differs  from  other  soft  black  minerals  in 
cutting  like  wax  and  in  yielding  malleable  silver  on  heating.  Dif- 
fers from  cerargyrite  in  solubility  in  nitric  acid. 

REMARKS. — Occurs  sparingly  with  other  silver  minerals  as  pure  material,  but  is 
probably  the  compound  of  silver  so  frequently  included  in  galenite,  sphalerite,  etc. 
Large  amounts  of  argentite  have  been  obtained  in  Nevada,  especially  from  the  Corn- 
stock  lode  and  the  Austin  mines.  Also  in  Arizona.  It  is  a  common  ore  in  Mexico, 
Chili,  Peru  and  Bolivia. 

USES. — It  is  an  ore  of  silver. 

STROMEYERITE. 

COMPOSITION.  —  CuAg  S,  (Ag  53.1  ;  Cu  31.1  per  cent.). 

GENERAL  DESCRIPTION.  —  Dark  gray  metallic  masses  resembling  chalcocite.  Rarely 
twinned  orthorhombic  crystals. 

PHYSICAL  CHARACTERS.  —  Opaque.  Lustre,  metallic.  Color,  dark  gray.  Streak, 
same  as  color.  H.,  2.5-3.  Sp.  gr.  6.2-6.3. 

BEFORE  BLOWPIPE,  ETC.  —  Reacts  for  copper,  silver  and  sulphur. 

HESSITE. 

COMPOSITION. — (Ag-Au)2Te,  grading  from  hessite,  Ag2Te  (Ag  63 
per  cent.)  to  petzite,  in  which  there  is  20  to  25  per  cent,  of  gold. 

GENERAL  DESCRIPTION. — Fine-grained,  gray,  massive  mineral, 
of  metallic  lustre.  Also  coarse  granular,  and  in  small,  indistinct, 
isometric  crystals. 

Physical  Characters.     H.,  2  to  2.5.     Sp.  Gr.,  8.3  to  8.6. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  black.  TENACITY,  slightly  sectile. 

COLOR,  between  steel  gray  and  lead  gray. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal,  fuses  to  a  black  globule, 
with  white  silver  points  on  its  surface.  If  powdered  and  dropped 
into  boiling  concentrated  sulphuric  acid,  the  acid  is  colored  an 
intense  purple. 


MERCURY  AND   SILVER   MINERALS.  299 

PROUSTITE.— Light  Ruby  Silver. 

COMPOSITION.— Ag3AsS3,  (Ag  65.4,  As  15.2,  S  19.4  per  cent.). 
Sometimes  containing  a  little  antimony. 

GENERAL  DESCRIPTION. — A  scarlet  vermilion  mineral,  either 
translucent  or  transparent,  with  a  scarlet  streak.  Usually  occurs 
disseminated  through  the  gangue  or  as  a  stain  or  crust.  Rarely 
in  small  hexagonal  crystals. 

CRYSTALLIZATION. —  Hexagonal.    Hemimorphic 
class,   p.  46.     Axis    c  =  0.804.      Fig.    412    shows   a      FlGi  412- 
typical  crystal  according  to  Miers.     Optically  — ,  with 
very  high    indices    of  refraction    (j  =  2.979    f°r 
light). 

Physical  Characters.      H.,    2   to   2.5.     Sp.   gr.,   5.57 
to  5.64. 

LUSTRE,  adamantine,  brilliant.      TRANSLUCENT  to  transparent. 
STREAK,  scarlet.  TENACITY,  brittle. 

COLOR,  scarlet  vermilion. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal,  fuses,  yields  sulphurous 
and  garlic  odors  and  malleable  silver.  In  closed  tube,  fuses  and 
yields  slight  red  sublimate,  yellow  when  cold.  Decomposed  by 
nitric  acid,  leaving  a  white  residue.  In  powder,  is  turned  black  by 
potassium  hydroxide  solution,  and  partially  dissolved  on  boiling. 
Hydrochloric  acid  precipitates  from  this  a  lemon  yellow  arsenic 
sulphide. 

SIMILAR  SPECIES. — Differs  from  pyrargyrite  in  scarlet  streak, 
and  from  cuprite  and  cinnabar  by  garlic  odor  when  heated. 

REMARKS. — Occurs  with  other 'silver  minerals,  and  is  mined  as  an  ore  of  silver. 
Most  abundant  in  the  United  States  at  Poor  Man's  Lode,  Idaho  ;  Austin,  Nevada,  and 
in  Gunnison  County,.  Colorado,  at  the  Ruby  silver  district ;  in  large  quantities  at 
Guanajuato,  Mexico;  at  Chanarcillo,  Chili,  and  other  South  American  localities. 
Noted  European  localities  are  Andreasberg,  Freiberg,  and  Joachimsthal  in  the  Harz. 

PYRARGYRITE.— Dark  Ruby  Silver. 

COMPOSITION. — Ag3SbS3,  (Ag  59.9,  Sb  22.3,  S  17.8  per  cent.). 
Often  with  small  amounts  of  arsenic. 

GENERAL  DESCRIPTION. — A  nearly  black  mineral,  which  is  deep 
red  by  transmitted  light  and  has  a  purplish-red  streak.  Usually 
occurs  massive  or  disseminated,  or  in  thin  films,  sometimes  in 
crystals. 


300  DESCRIPTIVE  MINERALOGY. 

FIG.  413.  CRYSTALLIZATION.  —  Hexagonal.     Hemimorphic 

class,  p.  46.  Axis  ^=0.789.  Prismatic  crystals, 
with  rhombohedral  or  scalenohedral  terminations. 
Frequently  twinned.  Fig.  413  shows  a  typical 
crystal  according  to  Miers.  Optically  — ,  with  very 
high  indices  of  refraction  (j  =  3.084  for  red  light). 

Physical  Characters.     H.,  2.5.     Sp.  gr.,  5.77  to  5.86. 

LUSTRE,  metallic,  adamantine.  TRANSLUCENT  to  opaque. 

STREAK,  purplish  red.  TENACITY,  brittle. 

COLOR,  black  or  nearly  so,  but  purple  red  by  transmitted  light. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal,  fuses  easily,  spirts, 
evolves  dense  white  fumes  and  leaves  malleable  silver.  A  white 
sublimate  forms.  In  closed  tube,  yields  black  sublimate,  red 
when  cold.  Soluble  in  nitric  acid,  with  separation  of  sulphur 
and  antimony  trioxide.  In  powder,  is  turned  black  by  a  solution 
of  potassium  hydroxide,  and  on  boiling  it  is  decomposed  ;  the  solu- 
tion deposits  an  orange  precipitate  on  addition  of  hydrochloric 
acid. 

SIMILAR  SPECIES.  —  The  streak  is  purplish  red,  differing  from  the 
scarlet  of  proustite.  The  streak  and  silver  reaction  distinguish  it 
from  cuprite,  cinnabar  and  realgar. 

REMARKS — Occurs  with  other  silver  minerals  and  with  arsenic,  arsenopyrite,  tetra- 
hedrite,  galenite,  etc.  Localities  same  as  for  proustite,  with  which  it  is  usually  asso- 
ciated. 

USES. — It  is  an  important  ore  of  silver. 

STEPHANITE.— Brittle  Silver  Ore. 

COMPOSITION.— Ag5SbS4,    (Ag  68.5,  Sb  15.2,  S  16.3  per  cent). 

GENERAL  DESCRIPTION. — Fine-grained,  iron-black  mineral,  with 
metallic  lustre,  often  disseminated  through  the  gangue.  Some- 
times in  short  six-sided  prismatic  crystals.  It  is  soft,  but  brittle. 

CRYSTALLIZATION.  —  Orthorhombic.       Axes 
&\~b:c  =  0.629  :    l  :  0.685.     Short    prismatic  J^'  4I41 

crystals  often  twinned  in  pseudo-hexagonal 
shapes.  Unit  pyramid  p,  unit  prism  ;;/,  the 
pinacoids  b  and  c  and  the  dome  /=  (oo  d  : 
1  :  2c) ;  {021}  ;  are  the  commoner  forms.  Sup- 
plement angles  mm  ==  64°  21'  ;  // =  49°  44'  ;  cf =  53°  53'. 


MERCURY  AND   SILVER  MINERALS,  30 1 

Physical  Characters.     H.,  2  to  2.5.     Sp.  gr.,  6.2  to  6.3. 
LUSTRE,  metallic.  OPAQUE. 

STREAK  and  COLOR,  black.  TENACITY,  brittle. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal,  fuses  easily,  yielding 
white  fumes  and  coat  and  odor  of  sulphur  dioxide,  finally  leaves 
malleable  silver.  Soluble  in  nitric  acid,  with  residue  of  sulphur 
and  antimony  trioxide.  With  potassium  hydroxide,  reacts  like 
pyrargyrite. 

SIMILAR  SPECIES. — It  is  more  brittle  than  argentite  and  softer 
than  tetrahedrite. 

REMARKS. — Occurs  with  other  silver  ores.  It  is  of  common  occurrence  in  the  Ne- 
vadasilver  mines,  and  also  at  Guanajuanto,  Mexico,  and  at  Chanarcillo,  Chili.  Found 
also  in  the  mines  of  Idaho  and  in  those  of  Saxony,  Bohemia  and  Hungary. 

POLYBASITE. 

COMPOSITION.— (Ag.Cu)9SbS6,  often  with  some  Sb  replaced  by  As. 

GENERAL  DESCRIPTION. — A  soft,  iron-black  mineral,  of  metallic  lustre,  best  known 
in  six-sided  tabular  prisms,  with  bevelled  edges.  In  thin  splinters  it  is  cherry  red  by 
transmitted  light.  Orthorhombic. 

PHYSICAL  CHARACTERS.— Nearly  opaque.  Lustre  metallic.  Color  and  streak, 
black.  H.,  2  to  3.  Sp.  gr.,  6  to  6.2.  Brittle. 

BEFORE  BLOWPIPE,  ETC  —Fuses  with  spirting.  Gives  off  odor  of  garlic  sometimes, 
but  always  yields  heavy  white  fumes  and  odor  of  sulphur  dioxide,  and  leaves  malleable 
button,  which  in  beads  reacts  for  copper,  or,  if  dissolved  in  nitric  acid,  will  yield  a 
flocculent  white  precipitate  on  addition  of  hydrochloric  acid.  In  closed  tube,  fuses 
very  easily,  but  yields  no  sublimate.  Soluble  in  nitric  acid. 

CERARGYRITE.-Horn  Silver. 

COMPOSITION.— AgCl,    ( Ag  7 5 . 3  per  cent.). 

GENERAL  DESCRIPTION.— A  soft,  grayish-green  to  violet  crust 
or  coating  of  the  consistency  and  lustre  of  horn  or  wax.  Rarely 
in  cubic  crystals. 

X 
Physical  Characters.     H.,  I  to  1.5.     Sp.  gr.,  5  to  5.5. 

LUSTRE,  waxy,  resinous.  TRANSLUCENT. 

STREAK,  shining  white.  TENACITY,  very  sectile. 

COLOR,  pearl  gray  or  greenish,  darkens  on  exposure  to  light, 
becoming  violet,  brown  or  black. 

BEFORE  BLOWPIPE,  ETC.— Fuses  very  easily,  yields  acrid  fumes 
and  a  globule  of  silver.  Rubbed  on  a  moistened  surface  of  zinc 


302  DESCRIPTIVE  MINERALOGY. 

or  iron,  it  swells,  blackens  and  the  surface  is  silvered,  and  the  min- 
eral is  reduced  to  spongy  metallic  silver.  In  matrass,  with  acid 
potassium  sulphate,  yields  a  globule,  yellow  hot,  white  cold,  and 
made  violet  or  gray  by  sunlight.  Insoluble  in  acids,  soluble  in  am- 
monia. On  coal,  with  oxide  of  copper,  yields  azure-blue  flame, 

SIMILAR  SPECIES. — Bromyrite,  embolite  and  iodyrite  are  most 
easily  distinguished  by  tests  with  acid  potassium  sulphate.  It 
differs  from  argentite  in  color  and  insolubility  in  nitric  acid. 

REMARKS.  —Occurs  usually  near  the  top  of  veins,  and  is  probably  precipitated  from 
silver-bearing  solutions  by  chlorides  in  surface  waters.  In  the  United  States  its  most 
celebrated  localities  have  been  Poor  Man's  Lode,  Horn  Silver  and  certain  Idaho  mines 
and  the  mines  at  Austin,  Nevada.  Found  also  in  proportionally  large  quantities  in 
many  of  the  Mexican  and  Chilian  mines. 

USES. — It  is  a  very  important  ore  of  silver. 

BROMYRITE.— Bromargyrite. 

COMPOSITION. — AgBr,   (Ag  57.4  per  cent.). 

GENERAL  DESCRIPTION. — Like  cerargyrite,  except  that  the  color  is  bright  yellow  to 
grass  green  or  olive  green.  H.,  2  to  3.  Sp.  gr.,  5.8  to  6.  Usually  found  in  small 
concretions  and  little  altered  by  exposure. 

BEFORE  BLOWPIPE,  ETC. — Like  cerargyrite,  except  that  in  matrass  with  acid  potas- 
sium sulphate  a  little  bromine  vapor  is  evolved,  coloring  the  fluid  salt  yellow,  and  the 
fused  bromyrite  sinks  as  a  dark  red,  transparent  globule,  which,  on  cooling,  becomes 
opaque  and  deep  yellow,  and  when  exposed  to  sunlight  becomes  dark  green. 

EMBOLITE. 

COMPOSITION.— Ag(Cl.Br).     Isomorphic  mixtures  of  the  chloride  and  bromide. 

GENERAL  DESCRIPTION. — Intermediate  between  cerargyrite  and  embolite.  Color, 
green  to  yellow,  darkening  on  exposure.  H.,  I  to  1.5.  Sp.  gr.,  5.31  to  5.81. 

BEFORE  BLOWPIPE,  ETC. — The  acid  potassium  sulphate  fusion  is  like  that  of  cerar- 
gyrite or  that  of  bromyrite,  as  the  bromine  is  small  in  amount  or  plentiful. 

IODYRITE  — lodargyrite. 

COMPOSITION. — Agl,    (Ag  46, 1  54  per  cent.). 

GENERAL  DESCRIPTION. — A  yellow  or  yellowish-green,  wax-like  mineral,  occurring 
massive  or  in  thin  flexible  scales  or  in  hexagonal  crystals. 

PHYSICAL  CHARACTERS.— Translucent.  Lustre,  resinous,  wax-like.  Color,  gray, 
yellow  or  yellowish  green.  Streak  yellow.  H.,  I.  Sp.  gr.,  5.6  to  5.7.  Sectile. 

BEFORE  BLOWPIPE,  ETC. — Fuses  very  easily,  spreads  out  and  gives  pungent  odor. 
In  closed  tube,  fuses  and  becomes  deep  orange  in  color,  but  cools  yellow.  With  oxide 
of  copper,  colors  flame  intense  green.  In  matrass  with  acid  potassium  sulphate,  yields 
violet  vapor  and  deep-red  globule,  which  is  yellow  when  cold  and  not  changed  by 
exposure  to  sunlight. 


CHAPTER   XXX. 

GOLD,  PLATINUM  AND  IRIDIUM  MINERALS. 
THE  GOLD  MINERALS. 

THE  minerals  described  are  : 

Metal  Gold  Au  Isometric 

Tellurides  Sylvanite  (Au.Ag)Te3  Monoclinic 

Calaverite  AuTe2 

Krennerite  AuTe2  Orthorhombic 

Aside  from  vein  and  placer  deposits  of  native  gold,  the  metal  is 
obtained  to  a  very  considerable  extent  from  the  minerals  pyrite, 
arsenopyrite  and  pyrrhotite,  and  from  other  sulphides  or  tellurides. 
In  1903  there  was  produced*  in  the  United  States  3,600,645  fine 
ounces  of  gold  worth  $74,425,340  which  was  nearly  one-fourth  of 
the  world's  production  of  $327,000,000.  About  three-fourths  of 
the  total  output  was  used  in  coinage  and  the  remainder  in  the  arts. 

A  large  proportion  of  the  world's  gold  is  found  in  superficial 
deposits  called  placers,  which  are  beds  of  sand,  gravel  or  boulders 
accumulated  from  the  erosion  of  higher  rocks  containing  gold 
veins.  In  working  shallow  placers  the  dirt  is  thrown  into  a  wooden 
trough  several  hundred  feet  long,  through  which  a  stream  of  water 
is  flowing.  At  the  bottom  of  the  trough  or  "sluice"  are  placed 
cross-bars  or  blocks  of  wood,  or  sometimes  a  pavement  of  flat 
stones  set  on  edge  is  constructed.  Near  the  head  of  the  sluice 
mercury  is  added  at  a  regular  rate,  and  this  encountering  the  gold 
unites  with  it,  and  the  heavy  gold  and  heavy  amalgam  are  caught 
in  the  interstices  of  the  wood  or  stone  pavement,  while  the  lighter 
material  is  washed  away.  At  intervals  the  stream  is  stopped,  the 
bars  or  blocks  removed  and  the  amalgam  collected.  By  heating 
in  a  retort  the  mercury  is  distilled  from  the  gold. 

Deep  placers  are  sometimes  treated  by  what  is  called  hydraulic 
mining,  which  differs  from  the  preceding  chiefly  in  the  magnitude 
of  the  work  and  the  fact  that  the  water  is  used  in  great  volume  and 
at  heavy  pressure,  not  simply  to  carry  the  material  down  the  sluice 
but  also  to  tear  down  and  wash  away  the  placer.  Frequently  this 

* Eng.  and  Min.  Jour.,  1904,  p.  4. 

3°3 


304  DESCRIPTIVE  MINERALOGY. 

is  preceded  by  driving  a  tunnel  into  the  bottom  of  the  placer  and 
exploding  heavy  charges  of  powder  to  loosen  the  gravel  bank. 

Gold  that  is  found  in  place  is  usually  in  quartz  veins  associated 
with  sulphides,  especially  pyrite.  It  is  extracted  by  finely  crush- 
ing the  vein  rock  and  collecting  the  gold  by  mercury  or  copper 
plates  coated  with  mercury.  The  vein  material  is  usually  stamped 
in  a  mortar  by  blows  of  several  pestles,  usually  five,  raised  suc- 
cessively by  cams  and  dropped.  Generally  water  and  mercury  are 
in  the  mortar,  and  as  the  material  becomes  sufficiently  fine  the 
water  carries  it  through  a  screen  over  a  series  of  amalgamated 
plates  which  catch  most  of  the  gold.  From  time  to  time  the 
amalgam  is  scraped  off  of  the  plates  and  collected  from  the  mortar 
and  retorted. 

Gold-bearing  pyrite  is  usually  stamped  as  described,  but  the 
residues  which  still  carry  some  gold  are  frequently  concentrated, 
roasted,  and  chlorinated.  Gold  tellurides  are  also  generally 
roasted,  ground  and  chlorinated.  That  is,  the  roasted  ore  is  sub- 
jected to  the  action  of  chlorine  and  the  gold  is  converted  into  a 
chloride,  soluble  in  water.  The  chlorine  may  be  generated  by  a 
mixture  of  salt,  pyrolusite  and  sulphuric  acid,  or  by  a  mixture 
of  sulphuric  acid  and  chloride  of  lime.  After  dissolving  out  the 
chloride  of  gold  with  water  the  gold  may  be  precipitated  as  metal 
by  ferrous  sulphate  or  as  sulphide  by  hydrogen  sulphide.  In  the 
latter  case  the  precipitate  is  pressed,  dried,  roasted,  and  finally 
fused. 

A  more  recent  method  is  to  submit  the  finely  crushed  ore,  which 
has  previously  been  roasted,  if  sulphide  or  telluride,  to  a  weak  so- 
lution of  potassium  cyanide.  With  the  aid  of  the  oxygen  of  the 
air,  or  of  some  oxidizing  agent,  the  potassium  cyanide  dissolves 
the  gold.  The  solution  is  then  drawn  off  into  large  vats  where 
the  gold  is  precipitated  by  means  of  zinc  turnings  or  the  gold  may 
be  separated  electrolytically.  The  method  has  become  of  the 
greatest  importance  and  comparatively  poor  ores  and  tailings  from 
the  amalgamation  process  are  very  successfully  treated  by  it. 

GOLD.  —  Native  Gold. 

COMPOSITION.  —  Au,  usually  alloyed  with  Ag,  and  sometimes 
Cu,  Bi,  Rh,  or  Pd. 

GENERAL  DESCRIPTION.  —  A  soft  malleable  metal  with  color  and 


GOLD,    PLATINUM  AND   IRIDIUM  MINERALS.         305 


streak  varying  from  golden  yellow  to  yellowish  white  according  to 
the  silver  contents.  It  is  found  in  nuggets,  grains,  or  scales,  us'ually 
so  disseminated  as  to  be  apparent  only  on  assay.  Rarely  in  dis- 
tinct isometric  crystals,  but  more  frequently  in  skeleton  crystals  or 


FIG.  415. 


Gold,  Butte  Co.,  Col.     Columbia  University. 

distorted  and  passing  into  wire-like,  net-like,  and  dendritic  shapes. 
Also  occurs  included  in  pyrite,  sphalerite,  galenite,  pyrrhotite,  and 
arsenopyrite. 

Physical  Characters.     H.,  2.5  to  3.     Sp.  gr.,  15.6  to  19.3. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  like  color.  TENACITY,  malleable. 

COLOR,  golden  yellow  to  nearly  silver  white. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  fuses  to  a  bright  yellow 
button  insoluble  except  in  aqua  regia.  Any  silver  present  will  sepa- 
rate from  the  solution  as  a  white  curd-like  precipitate.  If  the  solu- 
tion is  evaporated  to  a  thick  syrup  and  diluted  with  water  and 
heated  with  stannous  chloride  it  becomes  purple,  and  a  purple  pre- 
cipitate settles. 

SIMILAR  SPECIES. — Chalcopyrite,  pyrite,  and  scales  of  yellow 
mica  are  mistaken  for  gold,  but  differ  entirely  in  specific  gravity, 
streak,  brittleness,  and  solubility  in  acids. 


306  DESCRIPTIVE  MINERALOGY. 


REMARKS.—  Occurs  in  infinitesimal  amount  in  practically  all'rocks  and  soil,  and  even 
when  in  paying  quantities  is  commonly  only  revealed  by  an  assay.  The  solvent  action 
of  superheated  water  collects  and  redeposits  the  gold  in  more  concentrated  state,  usu- 
ally in  quartz  veins  associated  with  or  contained  in  pyrite,  arsenopyrite,  chalcopyrite, 
galenite,  pyrrhotite,  magnetite,  hematite,  bismuth,  tellurium  minerals,  etc.  It  is  prac- 
tically unchangeable,  but  the  wearing  away  of  the  containing  rocks  and  the  sorting 
and  transportation  of  the  fragments  with  the  solution  of  the  solvent  portions  results  in 
the  formation  of  gold-bearing  gravels,  river  beds,  etc. 

The  four  largest  gold  producing  States  are  California,  Colorado,  South  Dakota  and 
Montana.  Besides  these  American  localities  the  mines  of  Victoria  and  New  South 
Wales,  Australia,  those  on  the  eastern  coast  of  South  Africa,  and  the  Siberian  mines 
are  the  largest  gold  producers.  Many  other  countries  yield  smaller  amounts. 

USES.  —  The  chief  uses  are  for  coinage  and  jewelry. 


r  *~*~  -I 

THE   GOLD   TELLURIDES.  —  Sylvanite,  £Calaverite,   Krenneritey 

COMPOSITION.  —  Varying  from  sylvanite  (Au.Ag)Te2  to  calaverite 
or  krennerite,  AuTe2.  (Au  25  per  cent,  to  40  per  cent.) 

GENERAL  DESCRIPTION.  —  The  gold  tellurides  are  steel  gray  to 
silver  white  minerals,  sometimes  inclined  to  yellow.  They  are 
usually  found  incrusting  or  in  small  veins  in  the  gangue.  Sylvanite 
and  krennerite  are  found  at  times  in  small  crystals.  All  are 
made  yellow  by  heating. 

Physical  Characters.     H.,  1.5  to  2.5.     Sp.  Gr.  7.9  to  9.04. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  like  color.  TENACITY,  brittle. 

COLOR,  silver  white,  steel  gray  and  light  yellow. 

BEFORE  BLOWPIPE,  ETC.  —  On  charcoal  fuse  to  a  gray  button 
which  after  long  heating  yields  a  light  yellow  bead  of  gold  alloyed 
with  silver  which  is  soluble  in  aqua  regia  with  a  curd-like  white 
precipitate.  During  fusion  a  white  sublimate  forms  which  will 
color  the  flame  green,  but  which  if  scraped  together,  placed  on 
porcelain,  moistened  with  cone.  H2SO4  and  heated,  becomes  rose 
colored  or  violet.  In  the  open  tube  yields  a  white  sublimate  which 
melts  to  clear  transparent  drops.  Soluble  in  nitric  acid. 

REMARKS.  —  Gold  tellurides  are  the  chief  ores  of  the  Cripple 
Creek  district  in  Colorado  and  as  found  there  contain  but  little 
silver.  Tellurides  occur  also  in  other  localities  in  Colorado,  Cali- 
fornia, Hungary  and  New  South  Wales. 


GOLD,    PLATINUM  AND    IRIDIUAI  MINERALS.          JO/ 

THE    PLATINUM   AND    IRIDIUM    MINERALS. 

The  minerals  described  are  : 

Metal  Platinum  Pt  Isometric 

Iridosmine  (Ir.Os)  Hexagonal 

Arsenide  Sperrylite  PtAs2  Isometric 

Purified  platinum  is  largely  used  in  incandescent  lamps,  in  dental 
practice  for  attaching  artificial  teeth  to  the  plate,  in  laboratory  ap- 
paratus, in  stills  for  sulphuric  acid  and  to  a  more  limited  extent  in 
jewelry,  in  electrical  contact  points,  in  photography  for  platinotype 
prints,  in  the  so-called  "oxidizing  of  silver,"  and  in  the  balance 
wheels  of  non-magnetic  watches. 

The  greater  portion  of  the  metal  is  obtained  by  washing  placer 
deposits  in  the  Ural  Mountains,  and  only  a  little  is  obtained  from 
other  localities.  Russia  produced  234,878  ounces  in  1902.* 

Platinum,  as  it  occurs  in  nature,  is  always  alloyed  with  iron  and 
other  metals,  from  which  it  must  be  separated  before  it  possesses 
the  peculiar  properties  which  make  it  valuable.  The  native  min- 
eral is  first  treated  with  dilute  aqua  regia,  which  dissolves  out  any 
iron,  gold  or  copper.  Then  concentrated  aqua  regia  is  added  to 
the  residue,  and  the  platinum  and  a  small  amount  of  iridium  are 
brought  into  solution.  After  evaporation  of  the  excess  of  acid, 
ammonium  chloride  is  added,  the  ammonium-platinic  chloride  be- 
ing formed  and  also  a  small  amount  of  the  iridium  salt.  This  pre- 
cipitate, on  being  heated,  leaves  the  metal,  which  consists  almost 
wholly  of  platinum,  but  also  carries  a  small  amount  of  iridium. 
The  metals  can  be  further  separated,  but  for  many  purposes  this 
alloy  is  preferable  to  the  pure  platinum. 

The  mineral  iridosmine,  which  occurs  only  in  small  grains,  is 
used  for  pointing  gold  pens,  and,  by  fusion  with  phosphorus,  is 
converted  into  a  phosphide  of  iridium,  which  is  used  for  pointing 
tools  and  stylographic  pens,  for  draw-plates  for  gold  and  silver 
wire  and  for  knife  edges  in  the  most  delicate  balances. 

The  phosphide,  by  heating  in  a  bed  of  lime,  is  changed  to  pure 
iridium,  which,  alloyed  with  platinum,  is  used  for  the  standards 
of  weights  and  measures. 

A  process  of  iridium  plating  also  exists. 

*  Mineral  Industry,  1902,  p.  530. 


308  DESCRIPTIVE  MINERALOGY. 

PLATINUM.— Native  Platinum. 

COMPOSITION. — Pt(Fe),  usually  with  small  quantities  of  Rh,  Ir, 
Pd,  Os,  Cu,  and  nearly  always  with  Fe  even  as  high  as  one-sixth 
of  the  whole. 

GENERAL  DESCRIPTION. — A  malleable,  steel-gray  to  white  metal, 
occurring  in  small  grains  and  nuggets  in  alluvial  sands.  Very 
rarely  in  small  cubes. 

Physical  Characters.  H.,  4  to  4.5.     Sp.  gr.,  14  to  19. 
LUSTRE,  metallic.  OPAQUE. 

STREAK,  steel  gray.  TENACITY,  malleable. 

COLOR,  light  steel  gray.  Often  magnetic. 

BEFORE  BLOWPIPE,  ETC. — Infusible  and  unaffected  by  fluxes  or 
any  single  acid.  Soluble  in  aqua  regia. 

SIMILAR  SPECIES. — Heavier  than  silver  and  not  soluble  in  nitric 
acid. 

REMARKS. — Found  in  alluvial  deposits  with  other  refractory  minerals,  as  gold,  irid- 
osmine,  chromite,  corundum,  zircon,  diamond,  etc.  Is  said  to  occur  in  syenite  and  is 
sometimes  found  included  in  masses  of  chromite  or  of  serpentine.  By  far  the  larger 
part  of  the  platinum  of  commerce  is  obtained  from  placer  deposits  in  the  Ural 
mountains;  Borneo,  Brazil,  and  the  United  States  of  Colombia  also  produce  small 
amounts.  It  has  been  identified  in  many  of  the  gold  regions  of  the  United  States, 
but  only  in  small  quantities,  and  the  quantity  annually  produced  is  insignificant. 


Sperrylite.  —  PtAs2,  is  a  tin-white,  brittle  and  orkque  mineral  of  metallic  lustre 
and  is  chiefly  interesting  as  being  the  only  native  compound  of  platinum.  It  is  found 
in  minute  crystals  in  small  quantities  in  the  nickel  bearing  pyrrhotite  and  chalcopyrite 
of  Sudbury,  Canada,  and  in  the  cupric  sulphide,  covellite,  occurring  at  the  Rambler 
mine  in  Wyoming.  It  is  a  possible  future  source  of  platinum. 

IRIDOSMINE. 

COMPOSITION. — (Ir.Os),  sometimes  with  Rh,  Pt,  etc. 

GENERAL  DESCRIPTION. — A  tin-white  or  gray,  metallic  mineral,  very  hard  and 
heavy,  and  occurring  in  irregular,  flattened  grains  and  hexagonal  plates. 

PHYSICAL  CHARACTERS. — Opaque.  Lustre  metallic.  Color  and  streak,  tin  white 
or  gray.  H.,  6  to  7.  Sp.  gr.,  19. .3  to  21. 1.  Rather  brittle. 

BEFORE  BLOWPIPE,  Etc. — Infusible.  May  yield  unpleasant,  pungent  odor.  Insol- 
uble in  acids. 


CHAPTER   XXXI. 


POTASSIUM,  SODIUM,  LITHIUM  AND  AMMONIUM  MINERALS. 
THE    POTASSIUM   MINERALS. 


THE  minerals  described  are 


Chlorides 


Sulphates 
Nitrate 


Sylvite 
Carnallite 
Kainite 
Kali  nit e 
Nitre 


Isometric 

Orthorhombic 

Monoclinic 

Isometric 

Orthorhombic 


KC1 

KCl.MgCl.6H.jO 

KCl.MgSO4.3H2O 

K.A1(SO4)2.I2H.,O 

KNO3 

In  addition  to  these,  potassium  is  a  constituent  of  many  silicates, 
such  as  orthoclase  and  muscovite.  It  is  also  found  in  solution  in 
many  brines. 

The  natural  potash  salts,  especially  the  chlorides,  are  obtained 
in  large  amounts  from  two  or  three  deposits  in  Germany.  The 


Sylvite,  Stassfurt,  Germany.     U.  S.  National  Museum. 

present  annual  output  of  the  syndicate  controlling  these  mines  is 
over  3,000,000  tons  and  it  is  estimated  that  at  this  rate  of  produc- 
tion the  beds  will  last  for  thirty-three  centuries.  The  nitrate  is 

309 


310  DESCRIPTIVE  MINERALOGY. 

mined  in  India,  and  occurs  in  small  amounts  elsewhere.  Potas- 
sium bromide  is  extracted  from  the  mother  liquor  of  certain  brines. 
The  chief  important  uses  are  in  the  form  of  the  nitrate  in  gunpow- 
der and  as  the  chloride  or  sulphate  in  fertilizers.  The  element  is 
essential  to  plant  growth  and  is  liable  to  exhaustion  in  soils. 

SYLVITE. 

COMPOSITION.— KC1,    (K  52.4  per  cent.). 

GENERAL  DESCRIPTION. — Colorless,  transparent  cubes  or  white  masses,  which  look 
like  common  salt  and  have  somewhat  similar  taste.  Absorbs  moisture  and  becomes 
damp. 

PHYSICAL  CHARACTERS. — Transparent  when  pure.  Lustre,  vitreous.  Color,  color- 
less white,  bluish,  reddish.  Streak,  white.  H.,  2.  Sp.  gr.,  1.97  to  1.99.  Taste,  like 
salt.  Cleavage  in  cubes. 

BEFORE  BLOWPIPE,  ETC. — Fuses  very  readily,  coloring  flame  violet.  If  added  to  a 
salt  of  phosphorus  and  copper  oxide  bead,  the  flame  is  colored  azure  blue.  Soluble  in 
water  and  acids. 

CARNALLITE. 

COMPOSITION.— KCl.MgCl  +  6H.p  (K  14.1  percent.). 

GENERAL  DESCRIPTION.  —  A  massive  and  somewhat  granular  mineral  occurring  in 
beds  or  strata  at  the  Stassfurt  potash  salts  deposit  of  Germany.  Seldom  found  in 
crystals. 

PHYSICAL  CHARACTERS.  —  Translucent  to  transparent.  Lustre,  sub-vitreous.  Color, 
white,  brownish  and  reddish.  Streak,  white.  H.,  I.  G  —  1.62.  Taste,  salty  and 
bitter. 

BEFORE  BLOWPIPE,  ETC.  —  Same  as  for  sylvite.     Very  deliquescent. 
USES.  —  Is  the  chief  source  of  the  manufactured  potash  salts  of  commerce  which  are 
so  largely  used  as  fertilizers.     It  is  simply  dissolved  in  water  and  the  potassium  chloride 
crystallized  out  at  the  proper  temperature. 

KAINITE. 

COMPOSITION.  —  MgSO4.KCl  +  sH2O. 

GENERAL  DESCRIPTION.  —  White  to  dark  red  granular  crusts 
with  salty  taste,  also  tabular  and  prismatic  monoclinic  crystals. 

Physical  Characters.     H.,  2.5-3.     SP-  gr-  2.05-2.2. 

LUSTRE,  vitreous.  TRANSPARENT  to  translucent. 

STREAK,  colorless.  TASTE,  salty  and  astringent. 

COLOR,  white  to  reddish  white,  and  colorless. 

BEFORE  BLOWPIPE,  ETC.  —  Easily  fusible,  coloring  the  flame 
violet.  After  fusion  on  charcoal  in  reducing  flame  the  moistened 
mass  will  stain  bright  silve-.  Soluble  in  water. 

REMARKS.  —  Occurs  in  beds  of  considerable  thickness  in  Stass- 
furt, Germany,  with  halite,  sylvite,  and  other  soluble  salts. 


POTASSIUM,    SODIUM,    ETC.,    MIXERALS.  311 

Aphthitalite.  —  (K.Na)2SO4.     Thin  white  hexagonal  plates  or  crusts  on  Vesuvius 
lavas. 

KALINITE.  —  Potash  Alum. 


COMPOSITION.  —  KAl(SO4)2-f  1  2H2O,  (KjOg.g,  ALO3  10.8,  SO333.8, 
per  cent.  ). 

GENERAL  DESCRIPTION.  —  Natural  alum  with  the  peculiar  taste,  occurring  as  a  white 
efflorescence  on  argillaceous  minerals.  Usually  fibrous,  or  as  mealy  crusts,  or  compact. 

PHYSICAL  CHARACTERS.  —  Transparent  or  translucent.  Color,  white.  Lustre, 
vitreous.  Streak,  white.  Taste,  astringent.  Tenacity,  brittle.  H.,  2.5.  Sp.  gr.,  1.75. 

BEFORE  BLOWPIPE,  ETC.  —  On  heating,  becomes  liquid,  yields  water,  and  finally 
swells  to  a  white,  spongy,  easily-powdered  mass,  which  is  infusible,  but  colors  the  flame 
violet.  With  cobalt  solution,  becomes  deep  blue  on  heating.  Soluble  in  water. 

NITRE.—  Saltpetre. 

COMPOSITION.  —  KNO3,    (K2O  46.5,  N2O5  53.5  per  cent.). 

GENERAL  DESCRIPTION.  —  White  crusts,  needle-like,  orthorhom- 
bic  crystals  and  silky  tufts,  occurring  in  limestone  caverns  or  as 
incrustations  upon  the  earth's  surface  or  on  walls,  rocks,  etc.  Not 
altered  by  exposure. 

Physical  Characters.     H.,  2.  Sp.  gr.,  2.09  to  2.14. 
LUSTRE,  vitreous.  TRANSLUCENT. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  colorless,  white,  gray.  TASTE,  salty  and  cooling. 

BEFORE  BLOWPIPE,  ETC.  —  On  charcoal  fuses  easily,  deflagrates 
violently  like  gunpowder,  colors  the  flame  violet.  Soluble  in 
water. 


REMARKS.  —  Formed  in  certain  soils  by  the  action  of  a  ferment,  especially  after  rains. 
Although  found  in  small  quantity  in  many  of  the  so-called  alkali  lands  of  our  Western 
States,  it  is  not  utilized.  Deposits  in  Ceylon  and  India  are  worked,  and  refined  nitre 
produced,  but  almost  all  of  the  commercial  product  is  made  from  sodium  nitrate  and 
potassium  chloride. 

THE    SODIUM    MINERALS. 

The  minerals  described  are  : 

Chloride  Halite  NaCl  Isometric 

Sulphate  Mirabilite  Na2SO4.ioH,O  Monoclinic 

Nitrate  Soda  Nitre        NaNOs  Hexagonal 

Carbonate         Trona  NajCCvHNaCOj^H./)      Monoclinic 


Besides  which  sodium  is  an  important  constituent  in  plagioclase 
and  many  other  silicates. 


312  DESCRIPTIVE  MINERALOGY. 

HALITE,  or  common  salt,  occurs  in  beds  varying  from  a  few  feet 
to  over  three  thousand  feet  in  thickness.  It  occurs  also  in  nearly 
all  water,  from  infinitesimal  quantities  to  strong  brines,  and  it 
occurs  as  incrustations  on  high  planes  in  dry  regions.  The  salt 
deposits  are  mined  and  the  brines  are  pumped  up  and  evaporated 
by  the  heat  of  the  sun  or  by  artificial  heat.  Salt  to  the  amount 
of  23,849,221  barrels  was  reported*  as  produced  in  1902. 

The  amount  used  is  enormous;  for  instance,  over  1,000,000 
tons  per  year  are  converted  into  sodium  and  chlorine  compounds, 
chief  among  which  are  sodium  carbonate  and  bicarbonate,  caustic 
soda  and  bleaching  powder. 

BROMINE  is  present,  as  sodium  and  potassium  bromide,  in  many 
salt  deposits  but  makes  up  only  a  small  fraction  of  a  per  cent,  of  the 
total.  In  this  country  it  is  obtained  mainly  from  the  salt  wells  of 
Michigan  but  also  from  those  of  Ohio,  West  Virginia  and  Pennsyl- 
vania. In  1892  the  United  States  produced  513,890  pounds  of 
bromine  and  its  equivalent  in  potassium  bromide.f 

SODA  NITRE  is  found  in  enormous  quantities  at  Tarapaca,  Chili ; 
nearly  a  million  tons  a  year  are  exported.  It  is  used  in  the  manu- 
facture of  nitre  for  gunpowder,  in  the  production  of  nitric  acid,  but 
chiefly  for  fertilizing  purposes.  It  is  also  the  source  of  most  of 
the  IODINE,  as  the  mother  liquors  after  refining  may  contain  twenty 
per  cent,  of  sodium  iodate.  Large  deposits  exist  in  Death  Val- 
ley, California.  The  scarcity  of  water  makes  their  exploitation 
difficult. 

TRONA. — Carbonates  of  sodium,  mixed  carbonates,  and  bicarbo- 
nates  occur  plentifully  in  the  alkali  deserts  of  the  West  with  sul- 
phates and  chlorides.  The  pools  and  lakes  into  which  these  dis- 
tricts drain  contain  large  amounts  of  these  salts,  and  by  evaporating 
the  water  to  the  required  degree  of  concentration,  crystals  of  soda 
are  deposited,  which  are  refined  by  subsequent  operations. 

HALITE. — Rock  Salt,  Common  Salt. 

COMPOSITION.— NaCl,    (Na  60.6  per  cent.),  usually  impure. 

GENERAL  DESCRIPTION.— Essentially  colorless  to  white  and 
vitreous,  but  from  iron  is  frequently  brown  to  red.  It  occurs  in 
cubic  crystals,  often  with  cavernous  faces  and  in  masses,  with 
cubical  cleavage,  and  also  compact  granular  and  coarse  fibrous. 

*  Mineral  Industry,  1902,  p.  570. 
'f  Mineral  Resources,  1902,  p.  898. 


POTASSIUM,    SODIUM,    ETC.,    MINERALS. 


313 


In  dry  countries  it  occurs  as  a  fibrous  efflorescence.  It  is  liable 
to  absorb  moisture  and  becomes  damp,  especially  when  containing 
calcium  or  magnesium  chlorides.  It  is  known  by  its  taste. 


FIG.  417. 


FIG.  418. 


FIG.  419. 


FIG.  420. 


Physical  Characters.     H.,  2.5.     Sp.  gr.,  2.4  to  2.6. 

LUSTRE,  vitreous.  TRANSLUCENT  to  transparent. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white,  colorless,  yellow,  brown,  deep  blue. 
TASTE,  salt.  CLEAVAGE,  cubic. 

BEFORE  BLOWPIPE,  ETC.— Decrepitates  violently,  fuses  very 
easily  and  colors  the  flame  yellow  and  may  be  volatilized.  Easily 
soluble  in  cold  water. 

SIMILAR  SPECIES. — The  taste  distinguishes  it  from  all  other 
minerals. 

REMARKS. — Halite  occurs  with  rocks  of  all  ages  in  beds  of  great  thickness.  These 
are  formed  by  the  gradual  and  complete  evaporation  of  bodies  of  water  into  which  the 
salt  has  been  brought  in  small  increments  by  inflowing  streams.  Vast  lakes  and  seas 
of  salt  water  exist  in  different  parts  of  the  world  as  well  as  many  salt  springs. 

Innumerable  immense  deposits  of  salt  are  known  and  worked  in  almost  every 
civilized  country.  In  the  United  States  we  have  many  deposits.  Hundreds  of  square 
miles  of  central  and  western  New  York  are  underlaid  by  strata  of  salt  varying  from 
a  few  feet  to  one  or  two  hundred  feet  in  thickness.  Immense  amounts  of  salt  are  also 
produced  in  the  Saginaw  district  of  Michigan.  At  Petite  Anse,  La.,  salt  is  found  of 
such  purity  and  so  near  the  surface  that  it  is  simply  blasted  out  and  crushed  to  make 
it  ready  for  the  table.  The  supply  seems  to  be  inexhaustible.  In  the  southeastern 
part  of  Nevada  a  large  mountain  consists  mainly  of  salt.  Many  other  States  also 
produce  this  substance,  notably,  Kansas,  West  Virginia,  Ohio,  and  California. 

The  associates  are  other  minerals  produced  in  the  same  manner,  as  gypsum,  anhy- 
drite and  various  soluble  chlorides,  bromides  and  sulphates. 

USES.  —  Halite  is  used  in  immense  quantities  in  food  and  as  a 
preservative.  It  is  the  source  of  most  of  the  sodium,  sodium  car- 
bonate, and  other  sodium  compounds  of  commerce.  It  is  used  to 
glaze  pottery,  in  glass  and  soap  making,  and  in  many  metallurgical 
processes. 


3  H  DESCRIPTIVE  MINERALOGY. 

MIRABILITE.  —  Glauber  Salt. 

COMPOSITION.  —  Na2SO4  +  ioH2O  (Na2O  19.3,  SO3  24.8,  H2O 
55.9  per  cent). 

GENERAL  DESCRIPTION.  —  Translucent,  white,  fibrous  crusts  or 
monoclinic  crystals,  closely  resembling  those  of  pyroxene  in  form 
and  angle.  On  exposure  loses  water  and  falls  to  powder. 

Physical  Characters.     H.,  1.5  to  2.  Sp.  gr.,  1.48. 

LUSTRE,  vitreous.  TRANSPARENT  to  opaque. 

STREAK,  white.  TASTE,  salty  and  bitter. 
COLOR,  white  or  faintly  greenish. 

BEFORE  BLOWPIPE,  ETC.  —  On  charcoal  fuses,  colors  the  flame 
yellow  and  leaves  a  mass  which  will  stain  bright  silver.  In  closed 
tube  yields  much  water.  Easily  soluble  in  water. 

REMARKS. — Deposits  known  as  "lakes"  occur  near  Laramie,  Wyoming,  consist- 
ing of  mud  mixed  with  crystals  of  mirabilite  to  a  depth  of  2O  feet.  Mirabilite  separates 
also  from  the  Great  Salt  Lake,  Utah,  and  is  heaped  up  on  the  rhore  whenever  the  tem- 
perature falls  below  a  certain  point,  to  be  again  dissolved  in  the  summer.  Found  also 
at  the  bottom  of  the  Bay  of  Kara,  Caspian  Sea. 


Thenardite.  —  Na2SO4.     Twinned  tabular  orthorhombic  crystals  and  as  an  efflores- 
cence.     Soluble  in  water.      Found  at  Borax  Lake,  Cal.,  and  in  alkali  lands. 


Glauberite.  — Na2  SO4.CaSO4.  Tabular  monclinic  crystals  and  lamellar  masses  in 
rock  salt  and  in  the  mud  of  borax  lakes. 

SODA  NITRE.— Chili  Saltpetre. 

COMPOSITION. — NaNO3,    (Na2O  36.5,  N2O5  63.5  per  cent.). 

GENERAL  DESCRIPTION. — Rather  sectile  granular  masses  or  crusts 
of  white  color,  occurring  in  enormous  beds  and  as  an  efflorescence. 
Rarely  found  as  rhombohedral  crystals  of  the  forms  of  calcite.  On 
exposure  crumbles  to  powder. 

Physical  Characters.     H.,  1.5  to  2.     Sp.  gr.,  2.24  to  2.29. 
LUSTRE,  vitreous.  TRANSPARENT. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  colorless,  white  or  yellowish.    TASTE,  cooling  and  salty. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  deflagrates  less  violently 
than  nitre  and  becomes  liquid.  Colors  the  flame  yellow.  Very 
easily  soluble  in  water. 


POTASSIUM,    SODIUM,    ETC.,    MINERALS.  315 

REMARKS.  —  It  is  associated  with  salt,  gypsum,  and  many  soluble  salts.  There  is 
only  one  producing  locality,  the  celebrated  nitrate  fields  of  northern  Chili.  These 
fields,  however,  form  one  of  the  greatest  sources  of  wealth  to  that  nation.  Large  de- 
posits are  known  to  exist  in  Death  Valley,  Cal.,  and  smaller  deposits  exist  in  Nevada 
and  New  Mexico. 

USES. — It  is  used  in  manufacture  of  nitre  and  nitric  acid  in  large 
amounts,  and  also  in  fertilizers.  It  frequently  contains  sodium 
iodate  and  is  the  chief  source  of  the  iodine  of  commerce. 

TRONA.— Urao. 

COMPOSITION.— NajCCyNaHCOg  +  2H2O,   (Na2O  41.2,  CO2  38.9,  H2O  19.9.). 

GENERAL  DESCRIPTION. — Beds  and  thin  crusts  of  while  glistening  material,  often 
fibrous  and  occasionally  in  monoclinic  crystals.  It  is  not  altered  in  dry  air. 

PHYSICAL  CHARACTERS.— Translucent.  Lustre,  vitreous,  glistening.  Color,  white, 
gray,  yellowish.  Streak,  white.  H  ,  2.5  to  3.  Sp.  gr.,  2.H  to  2.14.  Taste,  alkaline. 

BEFORE  BLOWPIPE,  ETC. — Fuses  easily,  coloring  flame  yellow.  In  closed  tube 
yields  water  and  carbon  dioxide.  Easily  soluble  in  water.  Effervesces  vigorously 
in  cold  dilute  acids. 

Gay-Lussite. — Na2CO3.CaCO3.5H2O.  White  monoclinic  pyramidal  crystals  at 
Soda  Lake,  Nevada  ;  Venezuela,  etc. 


THE    LITHIUM   MINERALS. 

The  minerals  described  are  : 

Phosphate  Amblygonite  Li(Al.F)PO4,  Triclinic 

Silicates  Spodumene  LiAl(SiO3),j,  Monoclinic 

Lepidolite  R3Al(SiO,)3  Monoclinic 

The  metal  lithium  is  comparatively  rare  in  minerals  but  is  quite 
easily  detected  by  its  very  characteristic  line  in  the  red  of  the 
spectrum.  Its  salts  are  of  importance  in  medicine,  in  the  labor- 
atory, and  in  the  preparations  of  lithia  waters.  Effervescent  lithia 
tablets  are  an  effective  remedy  for  rheumatism. 

Large  deposits  of  the  lithium  minerals  occur  at  Pala,  California, 
and  all  the  species  mentioned  above  occur  there.  Spodumene  has 
also  been  mined  in  the  Black  Hills  of  South  Dakota.  Ambly- 
gonite is  also  produced  at  Montebras,  France.  In  1902  the 
amount  of  lithium  minerals  mined  in  this  country  was  1,245  tons* 
and  about  55,000  pounds  of  lithium  salts  were  consumed  of  which 
approximately  one  third  was  imported. 


*  Mineral  Resources  of '  U.  S.,  1902,  p.  261. 


316  DESCRIPTIVE  MINERALOGY. 

AMBLYGONITE. 

COMPOSITION.  — Li(Al.F)PO4,  (Li2O  10. i  per  cent,  generally  partly  replaced). 

GENERAL  DESCRIPTION.  —  A  cleavable  compact  massive  or  columnar  mineral  some- 
what resembling  orthoclase.  Sometimes  in  large  indistinct  crystals. 

PHYSICAL  CHARACTERS.  —  H  =  6,  Sp.  Gr.  =  3.01-3.09.  Lustre,  pearly  to 
vitreous.  Streak,  white.  Brittle.  Translucent.  Color,  usually  white,  sometimes 
with  green,  blue,  yellow  or  brown  tints. 

BEFORE  THE  BLOWPIPE,  ETC.  —  Gives  characteristic  red  lithia  flame,  fuses  with 
intumescence  to  an  opaque  white  globule.  Soluble  in  sulphuric  acid  when  powdered. 

REMARKS.  —  Occurs  in  quantity  at  Pala,  California. 

USES.  —  Is  an  important  source  of  lithium  and  carries  a  comparatively  high  percentage 
of  this  element. 

SPODUMENE. 

COMPOSITION. —  LiAl(SiO3)2,  Li2O  8.4  per  cent,  with  some  sodium 
replacing  lithium. 

GENERAL  DESCRIPTION. — White  or  greenish- 
white  monoclinic  crystals,  sometimes  of  enormous 
size,  more  rarely  small  emerald-green,  and  larger 
lilac  colored  crystals.  Also  in  masses.  Character- 
ized by  an  easy  parting  parallel  a  in  addition  to 
the  prismatic  cleavage. 

CRYSTALLIZATION.  —  Monoclinic.  Axes  a  :  1>  \ 
<:=  1.124  :  i  :  0.636 ;  fl  =  69°  40'  Common, 
forms  :  the  pinacoids  a  and  bt  the  unit  prism,  m, 
unit  pyramid  /,  the  pyramid  v  =  (a  :  b  :  2c]  ;  {221}  and  the 
clinodome  e  =  (oo  a  :  b  :  2c)\  (021 }.  Supplement  angles  :  mm  = 
93°;  pp  =  63°  31';  w  =  88°  34' ;  ee  =  107°  24'.  Optically  +  . 
Axial  plane  b. 

Physical  Characters.     H.,  6.5  to  7.     Sp.  gr.,  3.13  to  3.20. 
LUSTRE,  vitreous.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white,  pale-green,  emerald,  green,  pink,  purple. 

BEFORE  BLOWPIPE,  ETC. — Becomes  opaque,  intumesces,  swells 
and  fuses  to  a  white  or  colorless  glass,  coloring  the  flame  purple- 
red,  especially  with  hydrochloric  acid.  Insoluble  in  acids. 

SIMILAR  SPECIES. — Distinguished  by  its  tendency  to  split  into 
thin  pearly  plates  and  by  the  red  flame. 

REMARKS. — Occurs  in  granitic  rocks  with  garnet,  tourmaline  and  the  granite  min- 
erals, quartz,  feldspars  and  micas.  It  alters  readily  to  a  mechanical  mixture  of  albite 
and  mica.  Important  localities  are  Stony  Point,  N.  C. ;  Chesterfield  and  Huntington, 
Mass. ;  Branchville,  Conn. ;  Pennington  County,  S.  D. ,  Pala,  Cal. ,  etc. 


POTASSIUM,  SODIUM,  ETC.,  MINERALS.  317 

VARIETIES. 

Hiddenitc.  —  Small  transparent  emerald-green  crystals  from 
Alexander  Co.,  N.  C. 

Knnzite.  —  A  transparent  lilac  colored  spodumene  found  only 
at  Pala,  Cal. 

ALTERATIONS.  —  Spodumene  alters  to  /3  spodumene  by  replace- 
ment of  half  of  Li2O  by  Na2O  and  by  further  alteration  forms  cyma- 
tolite,  a  mixture  of  albite  and  muscovite. 

USES.  —  The  large  crystals  from  the  Etta  tin  mines,  South 
Dakota,  are  mined  as  a  source  of  lithium  salts.  The  varieties  hid- 
denite  and  kunzite  are  used  as  gems  and  the  latter  is  especially 
valued  for  its  intense  phosphorescent  properties  when  exposed  to 
x-rays,  ultra-violet  light  and  radium  emanations. 


LEPIDOLITE.  —  Lithia  Mica. 

COMPOSITION.  —  R3Al(SiO3)s.     R  —  Li,  K,  NaF,  etc.     Li2O,  4  to  6  per  cent. 

GENERAL  DESCRIPTION.  —  Scaly,  granular  masses  of  pale-pink  color  and  gray  trans- 
parent crystals,  with  easy  cleavage  into  elastic  plates. 

PHYSICAL  CHARACTERS.  —  Translucent.  Lustre,  pearly.  Color,  rose,  violet, 
lilac,  gray,  white.  Streak,  white.  H.,  2.5  to  4.  Sp.  gr.,  2.8  to  2.9.  Sectile. 
Cleavage,  basal. 

BEFORE  BLOWPIPE,  ETC.  —  Fuses  easily  to  a  white  glass.  Colors  the  flame  purple- 
red.  Partially  soluble  in  hydrochloric  acid. 

REMARKS.  —  Found  in  considerable  quantity  near  Pala,  San  Diego  Co.,  California, 
with  red  tourmaline,  also  at  Paris  and  Hebron,  Me.,  Chesterfield,  Mass.,  Rozena, 
Moravia,  Uto,  Sweden,  and  elsewhere. 

USES.  —  It  is  a  source  of  lithium  salts. 


THE    AMMONIUM    MINERALS. 

The  minerals  described  are  : 

Chloride  Sal  Ammoniac  NH4C1  Isometric 

Sulphate  Mascagnite  (NH4),SO4         Orthorhombic 

The  hypothetical  compound  radical  ammonium,  has  never  been 
separated  from  its  compounds.  Its  occurrence  in  nature  is  rare, 
and  its  minerals  while  of  great  theoretical  interest  do  not  occur  in 
commercial  quantities.  Its  compounds,  many  of  which  are  of 
great  importance  in  the  arts,  are  obtained  by  the  dry  distillation 
of  organic  matter,  and  notably  of  bituminous  coal  in  the  process 
of  gas  manufacture,  from  coke  ovens,  from  the  dry  distillation  of 
bones  and  from  the  gases  of  blast  furnaces  using  coal  as  fuel. 


318  DESCRIPTIVE  MINERALOGY, 

SAL  AMMONIAC. 

COMPOSITION.— NH4C1,    (NH4  33.7,  Cl  66.3  per  cent.). 

PHYSICAL  CHARACTERS.— Transparent  to  translucent.  Lustre,  vitreous.  Color, 
colorless,  white,  yellowish.  '  Streak,  white.  H.,  1.5  to  2.  Sp.  gr.,  1.53.  Taste, 
pungent,  salt.  Cleavage,  parallel  to  octahedron. 

BEFORE  BLOWPIPE,  ETC. — Sublimes,  without  fusion,  as  white  fumes.  With  soda 
or  quicklime,  gives  odor  of  ammouia.  Easily  soluble  in  water. 

REMARKS. — Occurs  near  volcanoes,  burning  coal-beds  and  in  guano  deposits. 
Artificially,  it  is  a  by-product  from  gas-works. 

MASCAGNITE. 

COMPOSITION.— (NH4)2SO4,     ((NH4)2O  39.4,  SO,  60  6  per  cent.). 

GENERAL  DESCRIPTION. — Yellowish,  mealy  incrustations  on  lava  or  in  guano. 
Rarely  in  orthorhombic  crystals. 

PHYSICAL  CHARACTERS. — Translucent.  Lustre,  dull  or  vitreous.  Color,  lemon- 
yellow,  yellowish  or  gray.  Streak,  white.  H.,  2  to  2.5.  Sp.  gr.,  1.76  to  1.77.  Taste, 
pungent  and  bitter. 

BEFORE  BLOWPIPE,  ETC. — Sublimes  without  fusion.  With  soda  or  quicklime,  yields 
odor  of  ammonia.  Easily  soluble  in  water. 

REMARKS. — Occurs  on  lava  or  guano  or  near  burning  coal-beds.  It  is  artificially 
made  from  the  ammoniacal  liquors  of  gas-works,  coke-ovens,  and  blast  furnaces  and 
to  a  less  extent  is  a  by  product  from  the  manufacture  of  bone  acid  in  Tuscany. 


CHAPTER   XXXII. 


BARIUM    AND    STRONTIUM   MINERALS. 
THE    BARIUM    MINERALS. 

THE  minerals  described  are  : 

Sulphate  Barite  BaSOi 

Carbonate  Witherite  BaCO3 

The  metal  occurs  also  in  a  few  silicates. 


Orthorhombic 
Orthorhombic 


In  the  elementary  state  barium  is  unimportant.  It  may  be  pre- 
pared by  the  electrolysis  of  its  chloride.  The  only  important 
mineral  compound  is  the  sulphate,  which  is  used  as  an  adulterant 
in  paint.  The  mineral  is  crushed  coarsely,  treated  with  sulphuric 
acid  to  remove  impurities,  washed,  pulverized  and  either  mixed  with 
white  lead  or  used  for  giving  weight  and  glaze  to  paper.  Nearly 
60,000  tons  were  mined  in  this  country  in  1902.  The  carbonate 
is  used  in  sugar  refining. 

BARITE.— Heavy  Spar. 

COMPOSITION. — BaSO4,  (BaO  65.7,  SO3  34.3  per  cent),  some- 
times with  some  strontia,  silica,  clay,  etc. 

GENERAL  DESCRIPTION. — A  heavy  white  or  light-colored  min- 
eral, vitreous  in  lustre.  It  occurs  in  Orthorhombic  crystals,  which 
are  frequently  united  by  their  broader  sides  in  crested  divergent 
groups,  and  varying  insensibly  from  this  to  masses  made  up  of 
curved  or  straight  lamellae  and  cleavable  into  rhombic  plates.  It 
occurs  also  granular,  fibrous,  earthy,  stalactitic  and  nodular. 
FIG.  422.  FIG.  423.  FIG.  424. 


FIG.  425. 


FIG.  426. 


FIG.  427. 


319 


320  DESCRIPTIVE  MINERALOGY. 

CRYSTALLIZATION.  —  Orthorhombic.  Axes  a  :  b  :  c  =  0.8 1 5  :  i  : 
1.314. 

Unit  prism  m,  base  c  and  domes  d  =  (cod  :  b  :  c]\  {oil}  and  n  = 
(d  :  co  ~b  \  \c)\  {102}  are  the  most  common  forms.  Supplement 
angles  are  mm  =  78°  23' ;  cd=  52°  43';  en  =  38°  52'. 

Optically  + .  The  axial  plane  parallel  b  and  the  acute  bisectrix 
normal  to  a.  Axial  angle  with  yellow  light  2^=  63°  12'. 

Physical  Characters.     H.,  2.5  to  3.5.     Sp.  gr.,  4.3  to  4.6. 
LUSTRE,  vitreous  and  pearly.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white  or  light  shades  of  yellow,  brown,  red  or  blue. 
CLEAVAGE,  basal  and  prismatic  (101°  37'  being  prism  angle). 

BEFORE  BLOWPIPE,  ETC — In  forceps,  decrepitates  and  fuses, 
coloring  the  flame  yellowish-green  and  leaving  an  alkaline  resi- 
due. With  soda,  on  charcoal,  gives  sulphur  reaction.  Insoluble 
in  acids. 

SIMILAR  SPECIES. — Distinguished  among  non-metallic  minerals 
by  its  high  specific  gravity,  insolubility  and  green  flame. 

REMARKS.  —  Frequently  found  in  veins  and  beds,  with  ores  of  antimony,  lead, 
copper,  iron,  etc. ;  also  as  veins  and  masses  in  limestones.  The  important  American 
localities  producing  barite  are  Madison  and  Gaston  Counties,  N.  C.,  Richlands,  Va. , 
and  Washington  Co.,  Mo.  Tennessee,  Connecticut,  Kentucky  and  Illinois  also  have 
extensive  deposits.  Some  barite  is  also  imported  from  abroad,  Germany  and  Hungary 
both  have  important  mines. 

USES.  —  The  white  variety  is  ground  and  used  as  an  adulterant 
of  white  lead  and  for  weighting  paper.  Colored  varieties  are  some- 
times cut  into  paper  weights,  vases,  etc.  Barite  is  also  made  into 
barium  chloride  and  hydrate. 

FIG.  428. 
WITHERITE. 

COMPOSITION.  —  BaCO3  (BaO  77.7,  CO2  22.3 
per  cent.). 

GENERAL  DESCRIPTION.  —  Heavy  white  or 
gray  translucent  masses  of  vitreous  lustre,  some- 
times with  small  indistinct  crystals  or  globular 
or  botryoidal  groups.  Also  granular,  columnar 
and  in  crystals  resembling  those  of  quartz. 

CRYSTALLIZATION.  —  Orthorhombic.        Axes     Cumberland,  Eng. 


BARIUM  AND   STRONTIUM  MINERALS.  321 

a  :  b  :  c  =  0.603  :  I  :  0.730.  Crystals  always  repeated  twins  re- 
sembling hexagonal  pyramids  with  usually  horizontal  striations  or 
deep  grooves  on  the  faces,  Fig.  428.  Optically  — . 

Physical  Characters.     H.,  3  to  4.  Sp.  gr.,  4.29  to  4.35. 
LUSTRE,  vitreous.  TRANSLUCENT. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white,  gray,  yellowish. 

BEFORE  BLOWPIPE,  ETC. — Fuses  rather  easily,  coloring  flame 
yellowish-green  and  becoming  alkaline.  Soluble  in  dilute  hydro- 
chloric acid,  with  effervescence,  and  less  rapidly  soluble  in  strong 
acid. 

SIMILAR  SPECIES. — Distinguished  by  its  weight,  effervescence 
with  acids  and  green  flame. 

REMARKS. — Occurs  in  veins  with  lead  ores  or  with  ores  of  silver  or  barite,  and  is 
probably  deposited  from  solution  in  water  containing  carbonic  acid.  Witherite  is  not 
mined  in  the  United  States,  although  small  deposits  occur  near  Lexington,  Ky.,  and 
on  the  north  shore  of  Lake  Superior.  The  most  productive  mines  are  at  Fallowfield 
in  England. 

USES.  —  As  an  adulterant  of  white  lead  and  in  refining  beet- 
sugar  molasses. 

Barytocalcite.  —  BaCaCO3.  Monoclinic  needles  and  masses  of  yellowish-white  color 
found  in  the  witherite  locality.  Always  yields  a  weak  manganese  test. 

THE    STRONTIUM   MINERALS. 

The  minerals  described  are  : 

Carbonate  Strontianite  SrCO3  Orthorhombic 

Sulphate  Celestite  SrSO4  Orthorhombic 

The  strontium  minerals  are  chiefly  of  use  to  form  strontium  salts 
used  as  precipitants  of  sugar  from  the  molasses  residues  of  the  beet 
sugar  industry,  and  in  the  manufacture  of  the  nitrate  for  use  in  the 
red  fire  of  fire  works. 

CELESTITE. 

COMPOSITION— SrSO4,    (SrO  56.4,  SO3  43.6  per  cent). 

GENERAL  DESCRIPTION. — A  white  translucent  mineral,  often  with 
a  faint  bluish  tinge.  Occurs  in  tabular  to  prismatic  Orthorhombic 
crystals,  fibrous  and  cleavable  masses,  and  rarely  granular.  It  is 
notably  heavy,  and  has  a  general  resemblance  to  barite. 


322 


DESCRIPTIVE  MINERALOGY. 


CRYSTALLIZATION.  —  Orthorhombic.  Axes  d  :  b  :  c  =  0.779  :  l 
:  1.280. 

The  common  forms  are  the  base  c,  the  unit  prism  ;;/  and  the 
•domes  n  and  o.  The  supplement  angles  are  mm  =75°  50'  ;  en  = 
39°  25';  co  =$2°. 


FIG.  429. 


FIG.  430. 


Sicily. 


Lake  Erie. 


Optically  -f  •  Axial  plane  b.  Acute  bisectrix  normal  to  a. 
Axial  angle  with  yellow  light  2E  =  88°  38'. 

Physical  Characters.     H.,  3  to  3.5.     Sp.  gr.,  3.95  to  3.97. 

LUSTRE,  vitreous  or  pearly.         TRANSPARENT,  nearly  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white  colorless,  pale  blue  or  reddish. 

CLEAVAGE. — Basal  and  prismatic,  yielding  rhombic  plates  in 
which  the  rhomb  angles  are  104°  10'  and  75°  50'. 

BEFORE  BLOWPIPE,  ETC. — Fuses  easily  to  a  white  pearly  glass 
and  colors  the  flame  crimson.  Usually  decrepitates  and  becomes 
alkaline.  With  soda  on  charcoal  gives  sulphur  reaction.  In- 
soluble in  acids. 

SIMILAR  SPECIES. — Distinguished  from  barite  by  its  red  flame 
and  from  other  minerals  by  its  high  specific  gravity,  insolubility 
and  red  flame. 

REMARKS. — Celestite  occurs  frequently  in  cavities  in  limestone,  marl  or  sandstone  or 
with  beds  of  gypsum  or  in  volcanic  regions  with  sulphur,  gypsum,  etc.  The  island  of 
Sicily  contains  the  most  celebrated  deposits  of  this  mineral,  and  is  the  chief  producing 
locality.  In  the  United  States  deposits  occur  on  Strontian  and  N.  Bass  Island,  Lake 
Erie,  at  Bell's  Mills,  Pa.,  at  Chaumont  Bay,  Lockport,  and  other  places  in  western 
New  York.  In  Kansas,  Texas,  West  Virginia  and  Tennessee,  also  at  Kingston, 
Canada. 

USES. — It  is  a  source  of  strontium  nitrate  used  to  make  crimson 
color  in  fireworks. 


BARIUM  AND   STRONTIUM  MINERALS.  323 

STRONTIANITE. 

COMPOSITION. — SrCO3,    (SrO  70.  i ,  CO2  29.9  per  cent.). 

GENERAL  DESCRIPTION. — Usually  found  as  yellowish- white  or 
greenish-white  masses  made  of  radiating  imperfect  needle  crystals 
and  spear-shaped  crystals,  very  like  those  of  aragonite.  Also 
fibrous  or  granular  and  only  rarely  in  distinct  orthorhombic  crys- 
tals, sometimes  of  considerable  size. 

Physical  Characters.     H.,  3  to  3.5      Sp.  gr.,  3.68  to  3.72. 

LUSTRE,  vitreous.  TRANSLUCENT. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  pale  yellowish  or  greenish-white,  also  green,  gray  and 
colorless. 

BEFORE  BLOWPIPE,  ETC. — In  forceps  swells,  sprouts,  colors  the 
flame  crimson,  fuses  on  the  edges  and  becoming  alkaline.  Soluble 
in  cold  dilute  acids  with  effervescence. 

SIMILAR  SPECIES. — Differs  from  calcite  and  aragonite  in  fusibility, 
higher  specific  gravity  and  purer  red  flame.  The  flame  and  effer- 
vescence distinguish  it  from  all  other  minerals. 

REMARKS.— Strontianite  is  found  in  the  United  States  chiefly  in  the  State  of  New 
York,  especially  at  Schoharie,  Muscalonge  Lake,  Chaumont  Bay,  Theresa  and  Clinton. 
Strontianite  used  in  the  German  beet  sugar  industry  is  largely  obtained  from  West- 
phalia. 

USES. — It  is  the  chief  source  of  the  strontium  salts  used  in  fire- 
works, and  is  also  converted  into  the  hydroxide  and  used  to  pre- 
cipitate sugar  from  molasses  as  a  strontium  compound  from  which 
crystalline  sugar  can  later  be  obtained. 


CHAPTER  XXXIII. 

CALCIUM  AND  MAGNESIUM  MINERALS. 
THE  CALCIUM  MINERALS. 

THE  minerals  described  are  : 

Fluoride  Fluorite  CaF2  Isometric 

Sulphates  Anhydrite  CaSO4  Orthorhombic 

Gypsum  CaSO4  -f  2HaO  Monoclinic 

Phosphate  Apatite  Ca5(Cl.F)(PO.,)3  Hexagonal 

Carbonates  Aragonite  CaCO3  Orthorhombic 

Calcite  CaCO3  Hexagonal 

Dolomite  CaCO3.MgCO3  Hexagonal 

Ankerite  (Ca.Mg.Fe)COs  Hexagonal 

Tungstate  Scheelite  CaWO4  Tetragonal 

Massive  CALCITE  and  DOLOMITE,  that  is  limestone  and  marble,  are 
quarried  in  enormous  quantities,  the  production  of  limestone  ex- 
ceeding in  value  even  that  of  granite. 

In  1902  there  was  produced  in  this  countiy  *  $5,044,182  worth 
of  marble,  while  of  limestone  the  value  was  :  for  building,  $5,563,- 
084 ;  as  lime,  $9,335,618  ;  for  roads,  $2,890,985  ;  for  railroad  bal- 
last, $2,661,081  ;  for  flux,  12,139,248  tons  valued  at  $5,271,252, 
and  for  other  purposes,  $4,508,983. 

In  addition  to  the  uses  enumerated  above,  limestone  is  used  for 
hydraulic  cements,  and  in  1903  f  8,200,000  barrels  of  natural 
hydraulic  cement  and  19,000,000  barrels  of  Portland  cement  were 
produced  in  the  United  States. 

GYPSUM  to  the  amount  of  816,478  tons  \  was  mined  in  this 
country  in  1902,  of  which  about  three  quarters  was  burned  to 
produce  plaster  of  Paris  and  wall  plaster,  and  the  remainder  was 
either  ground  and  used  as  land  plaster  or  sold  in  the  crude  state. 
There  has  been  a  greatly  increased  output  of  gypsum  mainly  from 
the  growing  use  of  the  calcined  product  as  wall  plaster  in  modern 
buildings  and  from  a  recent  use  of  ground  selenite  with  wood  pulp 


*  Mineral  Resources,  1902,  p.  698. 

I  Engineering  and  Mining  Journal,  1904,  p.  4. 

\  Mineral  Resources,  1902,  p.  903. 

324 


CALCIUM  AND  MAGNESIUM  MINERALS.  325 

in  paper  making.  About  3,000  tons  are  also  used  for  bedding  plate 
glass  during  the  grinding  process. 

APATITE  and  phosphate  rock  are  used  in  enormous  quantities 
for  the  manufacture  of  soluble  phosphates  for  fertilizers.  Florida, 
South  Carolina  and  Tennessee  produced  1,477,601  long  tons  of 
phosphate  rock  *  in  1903.  The  phosphoric  acid  is  rendered  avail- 
able for  the  use  of  plants  by  treating  the  rock  with  sulphuric  acid. 

FLUORITE  has  an  increasing  use  as  a  flux  in  melting  iron  and 
other  metallurgical  operations.  It  is  also  used  in  producing 
opalescent  glass  and  enamels  and  in  the  manufacture  of  hydro- 
fluoric acid.  In  1902  f  48,108  tons  were  mined  in  the  United 
States  mainly  from  Kentucky  and  Illinois. 

FLUORITE.  —  Fluor  Spar. 

COMPOSITION. — CaF2,    (Ca  51.1,  F  48.9  per  cent.). 

GENERAL  DESCRIPTION. — Usually  found  in  glassy  transparent 
cubes  or  cleavable  masses  of  some  decided  yellow,  green,  purple 
or  violet  color.  Less  frequently  granular  or  fibrous.  Massive 
varieties  are  often  banded  in  zigzag  strips  of  different  colors. 

FIG.  431. 

r~ 


Fluorite,  Cumberland,  England.     N.  Y.  State  Museum. 


*  Engineering  and  Mining  Journal,  1904,  p.  4. 
f  Mineral  Resources  of  'the  U.  S.,  1902,  p.  899. 


326 


DESCRIPTIVE  MINERALOG Y. 


CRYSTALLIZATION.  —  Isometric.  Usually  cubes  with  modifying 
forms,  especially  the  tetrahexahedron  e  =  (a  :  2a  :  co  a),  {210}; 
the  dodecahedron  d  and  the  hexoctahedron  t  =  (a:  2a  :  4^),  {42 1 } . 
The  cube  faces  are  often  striated  parallel  to  the  edges  or  with 
vicinal  faces,  p.  132,  giving  the  appearance  of  a  very  flat  tetra- 
hexahedron. Rarely  found  in  octahedrons,  sometimes  formed  by 


FIG.  432. 


FIG.  433. 


FIG.  434. 


a"' 


the  grouping  of  small  cubes  in  parallel  positions.      Penetration 
twins  common,  Fig.  43 1 . 

Index  of  refraction  for  yellow  light  1.4339. 
Physical  Characters.     H.,  4.     Sp.  gr.,  3.01  to  3.25. 

LUSTRE,  vitreous.  TRANSPARENT  to  nearly  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  wine-yellow,  green,  violet,  blue,  colorless,  brown,  black. 
CLEAVAGE,  octahedral. 

BEFORE  BLOWPIPE,  ETC.  —  In  closed  tube  at  a  low  heat  becomes 
phosphorescent.  In  forceps  fuses  to  a  white  opaque  glass  and 
colors  the  flame  red.  Soluble  in  hydrochloric  acid.  Heated  with 
acid  potassium  sulphate  or  sulphuric  acid,  fumes  are  set  free  which 
corrode  glass. 

SIMILAR  SPECIES. — Recognized  by  cleavage  and  crystals  and  by 
the  etching  test.  When  cut  it  may  resemble  aqua  marine,  yellow 
topaz,  etc.,  but  is  distinguished  by  softness. 

REMARKS. — Fluorite  may  have  been  deposited  from  solution  in  carbonated  waters. 
It  is  usually  found  in  veins  as  the  gangue  of  metallic  ores,  especially  lead,  silver, 
copper,  and  tin.  Sometimes  found  in  beds.  This  mineral  is  mined  in  large  quantities 
at  Rosiclare,  Illinois.  Found  in  smaller  amounts  in  Jefferson  and  Boulder  counties, 
Colo. ;  at  McComb  and  other  places  in  western  New  York.  In  many  localities 
throughout  New  England,  also  in  New  Jersey,  Arizona,  Virginia,  California  and  other 
States. 

USES. — It  is  used  as  a  flux  in  smelting  ores  ;  also  in  the  manu- 
facture of  opalescent  glass,  hydrofluoric  acid,  enamel  for  cooking 


CALCIUM  AND  MAGNESIUM  MINERALS.  327 

utensils,  and  the  brighter  colored  varieties  are  cut  into  vases,  figures 
or  imitation  gems.  Used  in  small  amounts  as  a  constituent  of  the 
bath  used  in  the  electrolytic  production  of  aluminium. 

ANHYDRITE. 

COMPOSITION. — CaSO4,    (CaO  41.2,  SO3  58.8  per  cent.). 

GENERAL  DESCRIPTION. — Granular,  marble-like  or  sugar-like 
in  texture,  or  as  fibrous  and  lamellar  masses  of  white,  gray,  bluish 
or  reddish  color.  Cleavage  in  three  directions  at  right  angles. 
Rarely  in  orthorhombic  crystals. 

Physical  Characters.     H.,  3  to  3.5.     Sp.  gr.,  2.9  to  2.98. 
LUSTRE,  vitreous  or  pearly.  TRANSLUCENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white,  gray, bluish,  brick-red.  CLEAVAGES  at  right  angles. 

FIG.  435. 


Gypsum,  Montmartre,  Paris,  France.     N.  Y.  State  Museum. 

BEFORE  BLOWPIPE,  ETC. — Fuses  to  a  white  enamel  and  colors 
the  flame  red.  With  soda  yields  a  sulphur  reaction.  Soluble 
slowly  in  acids. 

SIMILAR  SPECIES. — Differs  from  gypsum  in  being  harder  and 
not  yielding  decided  test  for  water.  Does  not  effervesce  in  acids 
like  marble.  Cleavage  pseudo-cubic. 

REMARKS.— Anhydrite  occurs  with  rock  salt,  limestone,  or  with  gypsum,  from 
which  it  may  have  been  formed  by  heat.  It  changes  to  gypsum  by  hydration,  often 
with  swelling  or  efflorescence.  The  chief  American  locality  is  at  Hillsboro,  New 


328 


DESCRIPTIVE  MINERALOGY. 


Brunswick.     Also  abundant  in  Nova  Scotia.     Found  in  smaller  quantity  at  Lockport, 
N.  Y.,  in  eastern  Pennsylvania  and  in  Tennessee. 

USES. — A  siliceous  variety  is  cut  and  polished  for  ornamental 
work.  Its  tendency  to  swell  prevents  its  use  in  building. 

GYPSUM.— Selenite,  Alabaster. 

COMPOSITION.— CaSO4  +  2  H2O,  (CaO  32.5,  H2O  20.9,  SO3  46.6 
per  cent.). 

GENERAL  DESCRIPTION. — Soft  colorless  white  or  slightly  tinted 
masses,  which  may  be  granular  or  compact,  or  may  be  translucent 
and  silky,  fibrous  or  transparent  and  cleavable  into  plates  and  strips. 
Also  in  transparent  cleavable  monoclinic  crystals. 


FIG.  436. 


FIG.  437. 


FIG.  438. 


FIG.  439. 


\x 


Utah. 


CRYSTALLIZATION.  —  Monoclinic.     /?  =  80°  42'.     Axes  a  : 


FIG.  440. 


Gypsum,  Ellsworth,   Ohio. 
Mineral  Co. 


Foote 


=  0.690  :  i :  0.412. 

Frequently  the  negative  unit  pyr- 
amid p,  with  the  unit  prism  m  and 
clino-pinacoid  b,  Figs.  437  and  440, 
or  these  twinned,  Fig.  438,  or  with 
dome  r  =  (a  :  oo  b  :  }^cj,  {103}  ; 
Figs.  436and439.  Supplement  angles 
mm=  68°  30'  ;  pp=  36°  12'  ;  cr 
=  11°  29'. 

Optically  -f  .  Axial  plane  at  or- 
dinary temperature  b,  but  with  higher 
temperatures  the  axial  angle  dimin- 
ishes and  the  axes  pass  into  a  plane 
at  right  angles  to  b,  the  axes  for  red 
light  so  passing  at  about  120°  C., 


CALCIUM  AND  MAGNESIUM  MINERALS.  329 

those  for  yellow  light  at  about   135°  C,  and  the  others  each  at 
a  definite  temperature. 

Physical  Characters.     H.,  1.5  to  2.     Sp.  gr.,  2.31  to  2.33. 

LUSTRE,  pearly,  silky,  vitreous.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle,  laminae  flexible. 

COLOR,  white,  colorless,  gray,  red,  yellow,  brown. 

CLEAVAGE,  clino-pinacoid  perfect,  unit  ortho-dome  fibrous,  and 
ortho-pinacoid  conchoidal.  The  cleavage  fragments  are  rhombic 
plates  with  angles  66°  and  114°. 

BEFORE  BLOWPIPE,  ETC.  — When  heated  quickly  becomes  white 
and  opaque  and  fuses  to  an  alkaline  globule,  coloring  the  flame 
yellowish-red.  In  closed  tube  yields  water.  Soluble  in  hydro- 
chloric acid.  The  powdered  dehydrated  mineral  when  mixed  with 
water  will  form  a  compact  mass.  Gives  sulphur  reaction. 

VARIETIES. 

Selenite. — Crystals  or  transparent  cleavable  masses. 

Satin  Spar. — Fine  translucent  fibrous  varieties  with  sheen  of 
silk. 

Alabaster. — Compact  and  fine  grained,  suitable  for  carving. 

Rock  Gypsum. — Scaly,  granular  or  dull  colored  and  compact. 

SIMILAR  SPECIES. — Talc,  brucite,  mica,  calcite,  heulandite,  stil- 
bite.  It  is  softer  than  all  but  talc,  lacks  the  greasy  feeling  of  talc 
and  is  further  characterized  by  quiet  solubility,  cleavages  and 
calcium  flame. 

REMARKS — Gypsum  occurs  in  large  beds  with  limestones,  marls,  and  clays,  and  in 
volcanic  regions  with  sulphur.  It  is  frequently  formed  by  the  action  of  the  sulphuric 
acid  from  decomposing  sulphides,  upon  calcareous  minerals.  It  is  also  formed  by  the 
dehydration  of  anhydrite,  by  the  evaporation  of  lakes  and  seas  and  by  the  action,  in 
volcanic  regions,  of  sulphurous  vapors  on  limestone. 

The  largest  producing  locality  in  the  United  States  is  in  the  region  of  Alabaster, 
Michigan.  Other  producing  localities  are  Ottawa  county,  Ohio,  Smith  and  Wash- 
ington counties,  Virginia,  Webster  county,  Iowa,  and  many  places  in  central  and 
western  New  York.  Deposits  of  gypsum  in  quantity  are  also  known  at  Scottsboro, 
Ala.,  Calcasien,  La.,  Royston's  Bluff,  Ark.  Also  in  Texas,  Colorado,  Kansas,  Mon- 
tana, Utah  and  most  of  the  other  States  and  Territories.  Large  quantities  are  annu- 
ally imported  from  New  Brunswick  and  Nova  Scotia.  Celebrated  deposits  also  occur 
in  Spain  and  Sicily. 

USES. — When  burned  and  ground  it  is  called  plaster-of-Paris. 
In  this  state  if  mixed  with  water,  it  becomes  hard  and  sets,  is  used 


330 


DESCRIPTIVE  MINERALOGY. 


for  the  production  of  casts,  moulds,  cements,  washes  and  the  hard 
finish  on  inside  walls  of  houses. 

Land  plaster  is  ground  gypsum,  and  is  used  on  soils.  Minor 
uses  are :  Satin  spar  for  cheap  jewelry,  selenite  in  optical  work  and 
alabaster  in  carving. 

APATITE.— Asparagus  Stone.     Phosphate  Rock. 
COMPOSITION.— Ca6(Cl.F)(PO4)3. 

GENERAL  DESCRIPTION. — Large  and   small  hexagonal  prisms, 

usually  of  green  or  red  color,  but  sometimes  violet,  white  or  yellow. 

Also   in   compact   varieties   which   are   commonly  dull-gray  or 

white,  rock-like  masses  or  nodules  not  unlike  common  limestone. 

FIG.  441.  FIG.  442.  FIG.  443. 


FIG.  444. 


FIG.  445. 


Paris,  Me.  Zillerthal. 

CRYSTALLIZATION.  —  Hexagonal.  Class  3  °  order  pyramid,  p.  5 1 . 
Axis  c  =  0.735.  Usually  the  unit  prism  m  terminated  by  the  unit 
pyramid  /  with  or  without  the  base  c.  More  rarely  the  second 
order  prism  a  or  the  flat  pyramid  o  =  (a  :  CD  a  :  a  :  %c),  {1012}, 
Fig.  445  ;  and  occasionally  third  order  pyramids,  as  t  =  (|#  :  40  : 
a  :|r),  {3143}.  Fig-  44^. 

Supplement  angles:  //  =  37°  44';  rr =  22°  31';  cp  =  40°  18'; 
cr=  22°  59'.  Optically  — ,  low  refraction,  weak  double  refraction. 

Physical  Characters.     H.,  4.5  to  5.     Sp.  gr.,  3.17  to  3.23. 

LUSTRE,  vitreous  to  resinous.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  green,  red,  brown,  yellow,  violet,  white,  colorless. 

CLEAVAGE,  imperfect  basal  and  prismatic. 


CALCIUM  AND  MAGNESIUM  MINERALS.  331 

BEFORE  BLOWPIPE,  ETC. — Fuses  with  difficulty  on  sharp  edges 
and  colors  the  flame  yellowish-red,  or,  if  moistened  with  concen- 
trated sulphuric  acid,  colors  the  flame  momentarily  bluish-green. 
Easily  soluble  in  hydrochloric  acid. 

If  to  ammonium  molybdate  in  nitric  acid  solution  a  few  drops 
of  a  nitric  acid  solution  of  apatite  be  added,  a  bright-yellow  pre- 
cipitate will  be  thrown  down  on  heating.  In  the  chlorine  variety 
silver  nitrate  will  produce  a  curdy  white  precipitate  in  the  nitric 
acid  solution. 

VARIETIES. — Certain  mineral  deposits  are  essentially  of  the  same 
composition  as  crystalline  apatite. 

Phosphorite. — Concretionary  masses,  with  fibrous  or  scaly  struc- 
ture. H  =  4.5. 

Osteolite. — Compact,  earthy,  impure  material,  of  white  or  gray 
color.  H.,  i  to  2. 

Phosphate  Rock  or  Nodules. — The  former  in  place  of  original 
deposition,  the  latter  chiefly  in  river  beds.  Massive,  gray,  white, 
brown  or  black.  H.,  2  to  5. 

Guano. — Granular  to  sponge-like  and  compact  material,  of  gray 
to  brown  color.  Sometimes  with  lamellar  structure. 

SIMILAR  SPECIES. — Green  crystals,  differ  from  beryl  in  lustre, 
hardness  and  solubility.  Red  crystals  differ  from  willemite  in 
not  gelatinizing  or  yielding  zinc. 

REMARKS. — Occurs  in  granites,  limestones,  tin  veins,  beds  of  iron  ore,  etc.,  fre- 
quently as  inclusions  in  other  minerals,  and  is  of  both  igneous  and  secondary  origin. 
The  most  productive  American  localities  for  the  pure  mineral  are  in  Ontario  and 
Quebec,  Canada;  Ottawa  County,  Quebec,  having  several  productive  mines.  Other 
deposits,  but  smaller  in  extent,  occur  at  Bolton,  Mass.;  Crown  Point,  N.  Y.,  and 
Hurdstown,  N.  J.  Immense  deposits  of  the  phosphate  rock,  so  largely  used  in  fer- 
tilizers, occur  in  eastern  South  Carolina  and  in  Florida ;  in  the  latter  case  underlying 
a  wide  belt  of  country  and  extending  through  several  counties  in  the  central  part  of 
the  State. 

USES. — The  massive  varieties  and  some  crystalline  deposits  fur- 
nish most  of  the  phosphates  for  fertilizers.  It  is  converted  into 
soluble  phosphates  by  treatment  with  sulphuric  acid,  in  which 
state  it  is  available  as  plant  food.  Apatite  is  also  used  in  the 
manufacture  of  phosphorus. 


Pharmacolite. — CaHAsO4.2H2O.     White  or  pink  silky  fibers  or  powders.     Yields 
garlic  odor  when  heated.     Occurs  with  arsenical  ores. 


332 


DESCRIPTIVE  MINERALOGY. 


ARAGONITE.  —  Flos  Ferri. 

COMPOSITION.  —  CaCO3,  (CaO  56.0,  CO2  44.0  per  cent). 

GENERAL  DESCRIPTION.  —  This  form  of  calcium  carbonate  is 
found  in  orthorhombic  crystals,  which  are  frequently  pseudo- 
hexagonal  from  twinning,  and  as  groups  of  acutely  terminated 
needle  crystals,  which  grade  into  fine  fibers.  It  also  occurs  stal- 
actitic,  incrusting  and  in  pure  white  groups  of  interlacing,  coral- 
like  stems.  The  prevailing  tint  is  white,  but  the  color  is  occasionally 
violet  or  pale  green. 

FIG  447.  FIG.  448.  FIG.  449.  FIG.  450. 


Bilin,  Bohemia.  Herrengrund. 

CRYSTALLIZATION.  —  Orthorhombic.  Axes d:~b\c  =  0.622  :  I  : 
0.721.  Occasionally  simple  crystals,  Fig.  447,  with  acute  domes 
and  pyramids  such  as  e  =  (coti  \~b  :  6c),  (06 1 }  ;  and  s  =  (|^  :  b  : 
6e),  {9.12.2}.  These  grade  into  needle-like  forms.  More  fre- 
quently twinned,  with  twin  plane  m,  giving  prisms  with  pseudo- 
hexagonal  cross  sections,  Figs.  449  and  450.  / 

Supplement   angles  are:    mm  =  63°    48';    dd=±7\°   33';    w 

=  130°   21'. 

Optically  — .  Axial  plane  a.  Acute  bisectrix  normal  to  c. 
Axial  angle  for  yellow  light,  2E=  30°  54'. 

Physical  Characters.     H.,  3.5  to  4.     Sp.  gr.,  2.93  to  2.95. 

LUSTRE,  vitreous.  TRANSLUCENT  or  transparent. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white,  violet,  yellow,  pale  green. 

CLEAVAGE. — Parallel  to  brachy  pinacoid,  prism,  and  brachy  dome. 

BEFORE  BLOWPIPE,  ETC. — Infusible,  colors  flame  red.  In  closed 
tube  decrepitates,  loses  weight  and  falls  to  pieces.  With  hydro- 
chloric acid,  dissolves  with  rapid  effervescence.  Powdered  and 
boiled  in  a  test-tube  with  dilute  cobalt  solution  aragonite  is  turned 
to  a  lilac  color. 


CALCIUM  AND  MAGNESIUM  MINERALS.  333 

SIMILAR  SPECIES. —  Natrolite  and  other  zeolites  which  occur  in 
needle  crystals  do  not  effervesce  in  acids.  Strontianite  and  wither- 
ite  have  higher  specific  gravity  and  are  fusible.  Calcite  has  a 
lower  specific  gravity,  differs  in  form,  cleaves  in  three  directions 
with  equal  ease  yielding  a  rhombohedron  of  105°  5',  and  in 
powder  is  unaffected  when  boiled  with  cobalt  solution. 

REMARKS. — Aragonite  is  largely  deposited  from  carbonated  water  solution  princi- 
pally in  rock  cavities  and  mineral  veins.  It  is  found  with  gypsum  and  in  beds  of 
serpentine  and  with  iron  ores  as  flos  ferri,  the  coraloidal  variety. 

It  can  be  changed  into  calcite  by  heat,  and  the  difference  between  it  and  calcite  is 
supposed  to  be  that  the  calcite  is  deposited  from  cold  solution  and  aragonite  from  hot 
solution.  It  is  not  of  common  occurrence,  but  is  found  at  Sulphur  Creek  and  Colton, 
California,  also  in  Solano  County,  Cal.  ;  in  Lockport  and  Edenville,  N.  Y. ;  in  Madi- 
son County,  N.  Y. ;  Haddam,  Ct. :  Warsaw,  111.,  etc. 


CALCITE. — Calcspar,  Limestone,  Marble,  Iceland 
Spar,  Etc. 

COMPOSITION. — CaCO3,    (CaO  56.0,  CO2  44.0  per  cent.). 

GENERAL  DESCRIPTION. — Yellowish  white  to  white  or  colorless, 
more  or  less  transparent  crystals,  usually  rhombohedrons  or  sca- 
lenohedrons.  Massive  with  easy  cleavage  or  coarse  to  fine- 
grained, stalactitic,  and  occasionally  fibrous,  lamellar  or  pulverulent. 

CRYSTALLIZATION.  —  Hexagonal.  Scalenohedral  class,  p.  42. 
Axis  c  =  0.854. 

Occurs  in  many  forms,  of  which  the  most  common  are  the 
rhombohedra:  /,  the  unit;  e  =  (a  :  oo  a  :  a  :  */£c\  {1012}  ;_/"  = 
(a  :  co  a  :  a  :  2c\  { 202  ij;  q  =  (a  :  oo  a  :  a  :  i6c),  { 16.0. 16.1}  ; 
the  scalenohedron :  v=\a\^a:a\  y,  and  the  unit  prism.  Twins 
are  frequent.  Supplement  angles  are//  =  74°  55'  ;  cc  =  45°  3' ; 
ff=  101°  9'  ;  qq  =  119°  24'.  The  polar  edges  w  are  75°  22' 
and  35°  36'. 

Optically  — .  With  very  strong  double  refraction,  but  weak  re- 
fraction (a  =  1.486  ;  f  =  1.658  for  yellow  light). 

Physical  Characters.     H.,  3.  Sp.  gr.,  2.71  to  2.72. 
LUSTRE,  vitreous  to  dull.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  yellow,  white,  colorless,  or  pale  shades  of  red,  green, 
blue,  etc. 


334  DESCRIPTIVE  MINERALOGY. 

FIG.  451.  FIG.  452.  FIG. 


FIG.  454. 


FIG.  457. 


FIG.  460. 


FIG.  455. 


Dog  Tooth  Spar,  Geikie. 


FIG.  458. 


FIG.  461.  FIG.  462. 


FIG.  456. 


FIG.  459. 


FIG.  463. 


CALCIUM  AND  MAGNESIUM  MINERALS.  335 

CLEAVAGE,  parallel  to  the  rhombohedron,  therefore  yielding  di- 
edral  angles  of  105°  5'  and  74°  55'. 

BEFORE  BLOWPIPE,  ETC. — Infusible.  Becomes  opaque  and  alka- 
line and  colors  flame  red.  Soluble  readily  in  cold  dilute  acids, 
with  vigorous  effervescence. 

VARIETIES. — The  following  are  the  most  prominent  varieties : 

Iceland  Spar. — Colorless,  transparent  crystals  and  masses. 

Dog  Tooth  Spar. — Scalenohedral  crystals,  supposed  to  resemble 
canine  teeth  in  shape. 

Fontainebleau  Sandstone. — Crystals  containing  up  to  60  per  cent, 
of  sand. 

Satin  Spar. — Fibrous,  with  silky  lustre. 

Argentine. — Foliated,  pearly  masses. 

Marble. — Coarse  to  fine  granular  masses,  crystalline. 

Limestone. — Dull,  compact  material,  not  composed  of  crystalline 
grains. 

Chalk. — Soft,  dull-white,  earthy  masses. 

Calcareous  Marl. — Soft,  earthy  and  intermixed  with  clay. 

Stalactites. — Icicle-like  cylinders  and  cones,  formed  by  partial 
evaporation  of  dripping  water. 

Stalagmite. — The  material  forming  under  the  drip  on  the  floor 
of  the  cavern. 

Travertine,  Onyx. — Deposits  from  springs  or  rivers,  "in  banded 
layers. 

Other  names,  such  as  Hydraulic  Limestone,  Lithographic  Lime- 
stone, Rock  Meat,  Plumbocalcite,  Spartaite,  etc.,  are  of  minor  im- 
portance, and  are  chiefly  based  on  color,  use,  locality,  etc.,  and 
do  not  generally  indicate  important  structural  or  chemical  dif- 
ferences. 

SIMILAR  SPECIES.— The  distinctions  from  aragonite  have  been 
given  under  that  mineral.  Dolomite  differs  in  slow  partial  solu- 
tion in  cold  dilute  acids,  instead  of  rapid  and  complete  efferves- 
cence. 

REMARKS.— Calcite  is  very  widely  distributed.  It  is  derived,  in  great  part,  from 
fossil  remains,  shells,  corals,  etc,  but  also,  in  considerable  part,  by  the  decomposition 
of  calcium  silicates  by  hot  carbonated  waters,  and  possibly,  in  a  degree,  by  the  action 
of  heat  on  aragonite.  The  carbonated  waters  deposit  aragonite  or  calcite,  according 
to  the  temperature  of  the  solution.  In  the  production  of  marble  Vermont  is  far  ahead 
of  any  other  State,  and  the  centre  of  the  industry  is  situated  at  Rutland.  Georgia 
and  Tennessee  also  produce  large  quantities,  especially  of  a  beautiful,  coarse,  granu- 
lar structure.  Alabama,  California,  New  York,  Pennsylvania  and  Massachusetts  also 


336  DESCRIPTIVE   MINERALOGY. 

have  large  deposits,  some  of  which  are  worked.  Crystallized  calcite  occurs  through- 
out the  world  in  all  limestone  regions.  In  the  United  States  these  localities  are  innu- 
merable and  transparent  varieties  are  common.  Rossie,  N.  Y.;  Warsaw,  111.,  and 
Llano  and  Lampasas  Counties,  Texas,  may  be  especially  noteworthy.  Fine  stalactites 
occur  in  the  caves  of  Virginia,  Kentucky  and  New  York.  Deposits  from  thermal 
springs  are  common  in  the  Yellowstone  Park,  and  similar  deposits  occurring  in  San 
Luis  Obispo  County,  California,  are  cut  and  polished,  yielding  slabs  of  onyx  marble 
of  extreme  beauty. 

USES.— Limestone  and  marble  are  important  building  stones, 
and  the  latter  is  also  used  for  statuary,  ornaments,  interior  work, 
tombstones,  etc.  Limestone,  again,  is  used  for  making  quicklime 
and  as  a  flux  in  smelting  siliceous  ore,  in  glass-making,  in  many 
chemical  processes,  in  hydraulic  cement,  as  a  lithographic  stone 
for  playing  marbles,  etc.  Iceland  spar  is  used  in  optical  apparatus 
for  polarizing  light. 


DOLOMITE. — Pearl  Spar,  Magnesian  Limestone. 

COMPOSITION*.  —  CaCO3.MgCO3  often  contains  iron  or  man- 
ganese. 

GENERAL  DESCRIPTION. — Small,  white,  pink  or  yellow,  rhombo- 
hedral  crystals,  usually  with  curved  faces,  or  more  frequently 
white,  massive  marble,  with  coarse  to  fine  grain  ;  or  gray,  white  and 
bluish,  compact  limestone. 

CRYSTALLIZATION.  —  Hexagonal,  class  of  third  order  rhombohe- 
dron,  p.  48.  Axis  c  =  0.832.  Usually  the  unit  rhombohedron 

FIG.  464.  FIG.  465. 


/,  Fig.  464,  the  faces  curved  or  doubly  curved  (saddle-shaped). 
Often  made  up  of  smaller  crystals.  Sometimes  the  more  acute 
rhombohedron  r  =  (a  :  oo  a  :  a  :  4*:),  {4041}.  Supplement  angles 
are//=  73°  45' ;  "-=  113°  53'. 

Optically—,  with  even  stronger  double  refraction  than  calcite. 


CALCIUM  AND  MAGNESIUM  MINERALS.  337 

Physical  Characters.     H.,  3.5  to  4.     Sp.  gr.,  2.8  to  2.9. 
LUSTRE,  vitreous  or  pearly.  TRANSLUCENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white,  pink,  greenish-gray,  brown  or  black. 
CLEAVAGE.     Rhombohedral.     Angles,  106°  15'  and  73°  45'. 

BEFORE  BLOWPIPE,  ETC. — Infusible,  colors  flame  yellowish -red 
and  becomes  alkaline.  With  cobalt  solution,  becomes  pink. 
Fragments  are  very  slightly  attacked  by  cold  dilute  acid.  The 
powdered  mineral  is  sometimes  attacked  vigorously  by  cold  dilute 
acid,  but  -sometimes  is  not.  On  heating  there  is  a  vigorous  effer- 
vescence. ,' 

SIMILAR  SPECIES. — Differs  from  calcite  in  effervescence,  color 
with  cobalt  solution  and  frequent  curvature  of  rhombohedral 
planes.  It  differs  from  siderite  and  ankerite  in  not  becoming 
magnetic  on  heating. 

REMARKS.— Dolomite  is  frequently  the  chief  constituent  of  whole  mountain  ranges 
and  may  have  formed ;  i.  From  a  solution  of  the  mixed  carbonates  of  calcium  and 
magnesium  in  carbonated  waters.  2.  From  calcite  by  infiltration  of  waters  contain- 
ing magnesium  carbonate.  3.  By  solution  of  part  of  calcium  carbonate  of  a  mag- 
nesian  limestone  in  preference  to  the  less  soluble  magnesium  carbonate,  thus  increas- 
ing the  proportion  of  the  latter.  Many  of  the  marbles  of  Vermont,  Georgia  and 
Tennessee  contain  magnesium,  and  frequently  enough  to  be  classed  under  dolomite. 
Crystals  are  common  in  many  localities,  especially  in  the  zinc  region  of  Missouri,  in 
many  places  in  the  limestone  region  of  Western  New  York,  in  the  gorge  at  Niagara, 
at  Glen  Falls  and  Brewsters,  N.  Y.,  at  Stony  Point,  N.  C. ;  Roxbury,  Vt.,  and  else- 
where. 

USES. — The  same  as  for  calcite.  The  dolomite  limestone  and 
marble  are  less  soluble  than  the  calcite  varieties,  and  are  to  that 
extent,  preferable  for  construction.  It  is  also  used  for  making 
epsom  salts  and  as  a  refractory  material  for  lining  converters  for 
the  basic  steel  processes. 

ANKERITE. 

COMPOSITION. — (Ca.Mg.Fe)CO3  sometimes  containing  manganese. 

GENERAL  DESCRIPTION. — Gray  to  brown  rhomboliedral  crystals  like  those  of  siderite, 
also  cleavable  and  granular  masses  and  compact. 

PHYSICAL  CHARACTERS. — Translucent  to  opaque.  Lustre,  vitreous  to  pearly.  Color, 
gray,  yellow  or  brown.  Streak,  white  or  nearly  so.  H.,  3.5  to  4.  Sp.  gr.,  2.95  to  3.1. 
Brittle.  Cleavage,  rhombohedral.  R  f\  R  =  106°  12'. 

BEFORE  BLOWPIPE,  ETC. — Infusible,  darkens  and  becomes  magnetic.     Soluble  in 
acids  with  effervescence. 
22 


338 


DESCRIPTIVE  MINERALOGY. 
SCHEELITE. 


COMPOSITION.— CaWO4,  (CaO  19.4,  WO3  80.6  per  cent.),  some- 
times with  replacement  by  molybdenum. 

GENERAL  DESCRIPTION. — Heavy  brownish  white  or  white  masses 
and  square  pyramids.  Also  drusy  crusts  of  yellow  or  brown 
crystals. 

FIG.  466.  FIG.  467.  FIG.  468. 


Schlackenwald. 


Trumbull,  Conn. 


CRYSTALLIZATION.  —  Tetragonal.  Class  of  third  order  pyramid, 
p.  41.  Axis  c  =  1.536. 

The  unit  first  order  pyramid  /  and  second  order  d  are  most 
common  with  sometimes  a  modifying  third  order  pyramid,  x  =  (a  : 
$a  :  3^),  {311}.  Supplement  angles  are  pp  =  79°  '55;  ^=72° 
40'. 

Optically  +. 

Physical  Characters.     H.,  4.5  to  5.     Sp.  gr.,  5.4  to  6.1. 

LUSTRE,  adamantine.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  pale  yellow,  gray,  brown,  white  or  green. 

CLEAVAGE,  distinct  parallel  to  first  order  pyramid,  indistinct 
parallel  to  second  order  pyramid. 

BEFORE  BLOWPIPE,  ETC.  —  Fusible  with  difficulty  on  sharp  edges. 
In  salt  of  phosphorus  forms  a  clear  bead  which  in  the  reducing 
flame  becomes  deep  blue,  and  if  the  bead  is  powdered  and  dis- 
solved in  dilute  hydrochloric  acid  it  yields  a  deep  blue  solution, 
especially  on  addition  of  metallic  tin.  Scheelite  is  soluble  in  hy- 
drochloric or  nitric  acid,  leaving  a  yellow  residue. 

SIMILAR  SPECIES. — Distinguished  among  non-metallic  minerals 
by  its  weight  and  behavior  in  salt  of  phosphorus. 


CALCIUM  AND  MAGNESIUM  MINERALS.  339 

REMARKS. — Scheelite  occurs  in  crystalline  rocks,  and  usually  with  cassiterite,  wolf- 
ramite, topaz,  fluorite,  molybdenite,  and  in  quartz.  It  changes  into  wolframite,  and 
also  forms  from  wolframite.  The  mineral  is  by  no  means  common,  but  is  found  at 
Monroe  and  Trumbull,  Conn. ;  Flowe  mine,  S.  C.,  in  Nevada,  Idaho,  and  Colorado 
Also  in  large  crystals  at  Marlow,  Quebec. 

USES. — Scheelite  is  used  as  a  source  of  tungsten,  which  has  im- 
portant properties  when  used  in  the  manufacture  of  ferro-tungsten 
and  tungsten  steel.  Other  applications  are  in  the  manufacture  of 
tungstic  acid,  from  which  a  yellow  pigment  is  obtained,  and  tung- 
state  of  soda,  which  renders  fabrics  almost  incombustible. 


THE    MAGNESIUM   MINERALS. 

The  minerals  described  are  : 

Hydroxide  Brucite  Mg(OH),  Hexagonal 

Sulphate  Epsomite  MgSO4.7H.iO  Orthorhombic 

Carbonate  Magnesite  MgCOs  Hexagonal 

Aluminate  Spinel  Mg(AlO2)2  Isometric 

Magnesia  is  also  the  principal  base  in  several  important  silicates, 
enstatite,  chrysolite,  serpentine,  talc,  etc.,  and  occurs  in  many 
others,  and  in  the  carbonate  dolomite. 

Over  50,000  tons  of  the  carbonate,  magnesite,  are  consumed 
annually  in  the  United  States.  The  hydroxide  and  sulphate  also 
occur  in  considerable  quantities. 

Calcined  magnesite  is  used  as  a  lining  for  the  converters  in  the 
basic  process  for  steel,  and  for  other  purposes  where  a  very  re- 
fractory material  is  desired.  Magnesite  is  the  favorite  source  of 
carbon  dioxide  in  seltzer  and  soda  water  manufacture,  as  the  treat- 
ment with  sulphuric  acid  leaves  a  residue  of  crude  epsom  salts 
which  can  be  recovered.  It  is  also  used  in  the  manufacture  of 
certain  kinds  of  wood-pulp  paper  and  as  a  covering  for  steam  pipes. 

The  metal  magnesium,  prepared  by  the  electrolysis  of  the  double 
chloride  of  potassium  and  magnesium,  and  purified  by  distillation 
out  of  contact  with  air,  is  now  made  in  quantity  in  the  shape 
of  ribbon  and  as  coarse  grains.  It  is  used  in  flash  lights  to  pro- 
duce a  vivid  light  for  photographing  in  absence  of  sunlight,  as  a 
reducing  agent  in  the  preparation  of  some  of  the  rarer  elements,  as 
a  purifying  agent  to  remove  the  last  traces  of  oxygen  from  copper, 
nickel  and  steel  and  as  a  dehydrating  agent  for  certain  oils  and  for 
alcohol.  The  metal  is  steadily  increasing  in  commercial  importance. 


340 


DESCRIPTIVE  MINERALOGY. 


BRUCITE. 

COMPOSITION.— Mg(OH)2,    (MgO  69.0,  H2O  31.0  per  cent.). 

GENERAL  DESCRIPTION. — White  or  gray  translucent  foliated 
masses  with  pearly  or  wax-like  lustre.  Also  fibrous  and  in  tabular 
hexagonal  crystals. 

Physical  Characters.  H.,  2.5.     Sp.  gr.,  2.38  to  2.4. 
LUSTRE,  pearly  or  wax-like.       TRANSLUCENT. 
STREAK,  white.  TENACITY,  sectile  and  flexible. 

COLOR,  white,  bluish,  greenish.    CLEAVAGE,  basal. 

BEFORE  BLOWPIPE,  ETC. — Infusible,  becomes  alkaline,  and  with 
cobalt  solution  becomes  pink.  Yields  water  in  closed  tube.  Solu- 
ble in  hydrochloric  acid. 

SIMILAR  SPECIES. — Harder  and  more  soluble  than  foliated  talc 
or  gypsum,  and  quite  infusible. 

REMARKS. — Brucite  is  usually  found  in  serpentine  or  limestone  with  magnesite  or 
hydromagnesite.  On  exposure  it  becomes  coatee"  with  a  white  powder,  and  is  some 
times  changed  to  serpentine  or  hydromagnesite.  its  most  prominent  American  locality 
is  at  Texas,  Pa.,  also  at  Fritz  Island  in  the  same  State;  at  Brewsters,  N.  Y..  and 
Hoboken,  N.  J. 

EPSOMITE.  —  Epsom  Salt. 
COMPOSITION.  —  MgSO  -f  7H2O,  (MgO  16.3,  SO3  32.5,  H,O  51.2  per  cent.). 

GENERAL  DESCRIPTION.  —A  delicate  white  fibrous  efflorescence 
FIG.  469.  or  earthy  white  crust  with  a  characteristic  bitter  taste.     Also  com- 

mon  in  solution  in  mineral  water.  Occasionally  in  crystals,  Fig. 
469,  which  are  noticeable  as  representing  class  of  the  sphenoid  in  the 
orthorhombic  system,  p.  35.  Optically — . 

PHYSICAL  CHARACTERS.  —  Transparent  or  translucent.  Lustre, 
vitreous  or  dull.  Color  and  streak,  white.  H.,  2  to  2.5.  Sp.  gr., 
1.75.  Taste,  bitter  and  salt. 

BEFORE  BLOWPIPE,  ETC.  —  Fuses  at  first,  but  becomes  infusible 
after  the  water  of  crystallization  has  been  driven  off.  With  cobalt 
solution  becomes  pink.  In  closed  tube  yields  acid  water.  Easily 
soluble  in  water. 

REMARKS.  —  Epsomite  is  formed  by  action  of  the  sulphuric  acid  of  decomposing 
sulphides,  upon  such  magnesian  minerals  as  serpentine  and  magnesite. 

MAGNESITE. 

COMPOSITION. — MgCOs,  (MgO  47.6,  CO2  52.4  per  cent),  with 
sometimes  iron  or  manganese  replacing  part  of  the  magnesium. 

GENERAL  DESCRIPTION. — White  chalk-like  lumps  and  veins  in 
serpentine.  Rarely  fibrous  or  in  rhombohedral  crystals  closely 
agreeing  with  dolomite  in  form  and  angle. 


CALCIUM  AND  MAGNESIUM  MINERALS. 


341 


Physical  Characters.     H.,  3.5 
LUSTRE,  dull,  vitreous  or  silky, 
STREAK,  white. 
COLOR,  white,  yellow,  brown. 


Sp.  gr.,  3  to  3.12. 
OPAQUE  to  translucent. 
TENACITY,  brittle. 
FRACTURE,  conchoidal. 


BEFORE  BLOWPIPE,  ETC.—  Infusible,  becomes  alkaline.  With 
cobalt  solution  becomes  pink.  Soluble  with  effervescence  in 
warm  hydrochloric  acid,  but  does  not  effervesce  in  cold  dilute 
acid.  No  decided  precipitate  is  produced  by  addition  of  sulphuric 
acid,  whereas  heavy  precipitates  form  with  solutions  of  calcite  and 
dolomite. 

SIMILAR  SPECIES.  —  Differs  from  dolomite  and  calcite  in  not 
yielding  the  calcium  flame. 

REMARKS.  —  Usually  formed  with  serpentine  by  action  of  carbonated  waters  on 
eruptive  magnesian  rocks,  such  as  olivine  (chrysolite),  or  when  the  decomposition  is 
carried  further  the  results  are  magnesite  and  quartz.  As  the  former  is  the  more 
common  decomposition,  magnesite  usually  occurs  with  serpentine  and  also  with 
other  magnesian  minerals,  such  as  talc,  brucite,  dolomite,  etc. 

Found  at  Bolton  and  Sutton,  Province  of  Quebec,  at  Texas,  Pa.,  Barehill,  Md.,  and 
at  several  localities  in  California  and  Massachusetts. 

USES.  —  It  is  used  in  the  lining  of  converters  in  the  basic  process 
for  steel,  and  for  lining  kilns  in  the  manufacture  of  sulphuric  acid 
and  for  other  purposes  where  a  non-conducting  and  refractory 
material  is  required,  especially  as  a  covering  for  steam  and  water 
pipes.  It  is  also  used  in  obtaining  carbon  dioxide  for  soda  water, 
the  residue  being  converted  into  epsom  salts.  Magnesia  and  mag- 
nesia alba  are  also  made  from  magnesite. 


SPINEL.  —  Balas  Ruby. 

COMPOSITION.  —  Mg(AlO2)2,  (MgO  28.2,  A12O3  71.8  per  cent). 
Iron,  manganese  and  chromium  are  sometimes  present. 


FIG.  470. 


FIG.  471. 


FIG.  472. 


342  DESCRIPTIVE  MINERALOGY. 

GENERAL  DESCRIPTION.— Usually  in  octahedral,  simple  or 
twinned  crystals,  which  cannot  be  scratched  by  steel  or  quartz 
and  vary  in  color  according  to  composition.  Also  in  rolled  peb- 
bles and  loose  crystals. 

CRYSTALLIZATION.  —  Isometric,  the  octahedron  p  or  this  modi- 
fied by  the  dodecahedron  d  or  the  trisoctahedron  o  =  (a  :  $a  :  3^)  ; 
(311).  Index  of  refraction  with  yellow-  light  1.7155. 

Physical  Characters.     H.,  8.     Sp.  gr.,  3.5  to  4.5. 

LUSTRE,  vitreous.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  red,  green,  blue,  black,  brown,  yellow. 
CLEAVAGE,  octahedral. 

BEFORE  BLOWPIPE,  ETC. — Infusible, 'oftwi  changing  color,  the 
red  variety  becomes  green,  then  nearly  colorless,  finally  red.  In 
powder  is  turned  blue  by  cobalt  solution.  Insoluble  in  hydro- 
chloric or  nitric  acid,  but  somewhat  soluble  in  sulphuric  acid. 

VARIETIES. —  "-*• 

Balas  Ruby  or  Ruby  Spinel  (Magnesia  Spinel). — Clear  red  or 
reddish,  often  transparent.  Sp.  gr.,  3.5  £0  3.6. 

Ceylonite  (Iron  Magnesia  Spinel). — Dark-green,  brown,  black, 
usually  opaque. 

Picotite  (Chrome  Spinel). — Yellowish  to  greenish-brown,  trans- 
lucent. 

SIMILAR  SPECIES. — Characterized  by  octahedral  crystals  and  by 
hardness. 

REMARKS. — Occurs  in  limestone,  serpentine,  gneiss,  etc.,  associated  with  corundum, 
chondrodite,  brucite,  etc  ,  and  sorrfetimes  changed  to  talc,  muscovite  or  serpentine. 
Gem  specimens  have  been  obtained  at  Hamburg,  N.  J.;  San  Luis  Obispo,  Cal.,  and 
Orange  County,  N.  Y.  The  crystals  also  occur  in  many  localities  in  North  Carolina, 
Massachusetts  and  near  the  New  York  and  New  Jersey  line.  Especially  abundant  in 
Ceylon  and  Burmah. 

USES. — Transparent  varieties  are  used  as  gems. 


CHAPTER   XXXIV. 


ALUMINUM  MINERALS. 


THE  minerals  described  are  : 

Fluoride 

Oxide 

Hydroxides 


Sulphates 


Phosphates 


Cryolite 

AlNa3F6 

Triclinic 

Corundum 

Ala08 

Hexagonal 

Bauxite 

A12O(OH)4 

Diaspore 

AIO(OH) 

Orthorhombic 

Gibbsite 

M(OH)3 

Monoclinic 

Alunogen 

Al2(S04)3.i8H20 

Monoclinic 

Aluminite 

(A1O^2SO4.9H2O 

Monoclinic 

Alunite 

K(A10H)3(S04)2  +  3H20 

Rhombohedral 

Turquois 

A12(OH)3P04.H20 

Wavellite 

A16(OH)6(P04)4  +  9H20 

Orthorhombic 

Beryllium- 
Aluminate          Chrysoberyl         BeAl2O4  Orthorhombic 

Aluminum  is  also  present  in  many  silicates,  and  is  an  essential 
constituent  of  all  clays. 

The  minerals  of  aluminum,  aside  from  the  clays,  have  important 
commercial  applications,  which  may  be  roughly  classified  as :  I. 
Ores  of  aluminum.      II.  Abrasive  materials.     III.   Gems. 
Ores  of  Aluminum. 

BAUXITE  to  the  amount  of  40,700  long  tons  was  mined  in  Georgia 
and  Alabama  in  1903,*  these  two  states  having  the  only  known 
American  deposits  of  importance.  This  ore  is  the  source  of  most 
of  the  aluminum  of  commerce  and  is  also  used  in  the  production 
of  alum  and  other  compounds  of  aluminum  used  extensively  in 
dyeing  and  calico  printing.  The  output  of  the  mineral  is  steadily 
increasing. 

GIBBSITE,  when  found  with  bauxite,  is  also  used  as  an  ore  but  is 
not  found  in  quantity.  Corundum  is  too  difficult  to  obtain  and  has 
too  high  a  value  as  abrasive  material,  and  the  abundant  clays  and 
silicates  contain  a  much  smaller  percentage  of  aluminum,  and  be- 
fore using,  need  to  be  decomposed  and  freed  from  silica. 

Metallic  aluminum,  formerly  prepared  only  by  reduction  of  the 
chloride  by  the  metal  sodium,  is  now  made  in  large  quantities 

*  Engineering  and  Mining  Journal,  1904,  p.  4. 
343 


344  DESCRIPTIVE  MINERALOGY. 

by  electrolysis.  In  1903  there  were  produced  in  this  country 
3,750*  tons  of  the  metal,  which  averaged  about  32  cents  per 
pound. 

The  ore  is  heated  with  sodium  carbonate  to  low  redness,  in 
order  to  produce  sodium  aluminate  without  rendering  the  silica 
or  iron  soluble.  On  dissolving  out  the  sodium  aluminate  with 
water  and  passing  carbon  dioxide  through  the  solution,  aluminum 
hydroxide  is  formed,  which  yields  the  oxide  when  heated.  By 
this  mode  of  procedure  most  of  the  iron  and  silicon  are  separated, 
which  would  otherwise  be  reduced  by  the  current  and  alloyed 
with  the  aluminum.  In  a  more  recent  process  the  impurities  in  the 
bauxite  are  removed  by  fusing  the  ore  with  carbon  in  an  electric 
furnace  whereby  iron,  silicon  and  titanium  are  reduced  or  converted 
into  carbides  'and  separate  on  top  of  the  aluminum  oxide  formed. 

For  the  production  of  the  pure  metal  the  oxide  is  decomposed 
by  electrolysis  in  a  fused  solvent  which  protects  the  metal  from 
contact  with  oxygen.  The  Hall  and  Heroult  processes  consist  in 
the  electrolysis  of  the  oxide  in  a  fused  bath  of  cryolite  or  the 
mixed  fluorides  of  sodium  and  aluminum.  The  Hall  process  is 
carried  on  in  iron  tanks,  the  bottom  and  sides  of  which  are  thickly 
lined  with  carbon.  The  tanks  serve  as  the  negative  electrodes 
and  are  filled  with  the  cryolite  flux,  to  which  a  little  fluorite  is 
added.  The  positive  electrodes  are  carbon  cylinders,  which  dip 
into  the  electrolyte. 

The  cylinders  are  first  lowered  until  they  touch  the  bottom  of 
the  tank,  and  the  ground  cryolite  is  melted  as  a  result  of  the  poor 
contact.  The  cylinders  are  then  raised,  and  the  current  thenceforth 
passes  through  the  melted  liquid.  The  alumina  is  now  added, 
and  is  immediately  dissolved  by  the  flux  and  decomposed  by  the 
current.  The  metal  settles  at  the  bottom  of  the  bath,  while  the 
oxygen  combines  with  the  carbon  of  the  anode  and  escapes  as 
carbon  dioxide.  The  metal  is  removed  from  time  to  time,  alumina 
is  again  added  and  thus  the  operation  is  continuous. 

Aluminum  is  used  where  lightness,  strength  and  non-corrosive- 
ness  are  desirable,  e.g.,  in  some  scientific  apparatus,  in  fancy  articles, 
to  a  limited  extent  in  cooking  utensils.  It  is  replacing  sheet  copper 
and  zinc,  and  is  used  as  bronze  powder  and  aluminum  leaf  for 
silvering  letters  and  signs.  It  is  of  growing  importance  as  a  sub- 


•  Engineering  and  Mining  Journal,  1904,  p.  3. 


ALUMINUM  MINERALS.  345 

stitute  for  stone  and  zinc  in  lithographing  and  is  used  in  large 
quantities  for  electrical  conductors.*  Aluminum  is  especially  son- 
orous and  is  now  used  in  the  Austrian  army  for  drums,  and  the 
substitution  of  aluminum  for  brass  in  the  other  band  instruments 
is  being  tried. 

Two  interesting  uses  of  aluminum  in  metallurgy  are  :  The  weld- 
ing of  wrought  iron  pipes,  rails  and  steel  castings,  in  place,  by  the 
heat  developed  by  oxidation  of  powdered  aluminum  mixed  with 
oxide  of  iron  (Thermite) ;  the  prevention  of  blow-holes  in  castings 
of  steel,  copper  or  zinc  by  the  addition  of  less  than  one  per  cent,  of 
aluminum  to  the  melted  metal. 

The  alloys  of  aluminum  are  extensively  used,  especially  the  alloy 
with  copper,  known  as  aluminum  bronze,  which  contains  usually 
as  much  as  ten  per  cent,  of  aluminum.  It  is  extremely  tough  and 
is  extensively  applied  in  machinery,  especially  mine  machinery, 
engine  castings,  etc.  The  alloys  with  zinc,  nickel  and  tin  are  also 
of  importance  and  to  some  extent  are  replacing  brass.  The  alloys 
with  zinc  are  malleable  and  ductile  and  when  chilled  possess  a  high 
tensile  strength.  Alloys  with  tungsten  are  also  growing  in  im- 
portance. 

CRYOLITE  to  the  amount  of  about  10,000  tons  per  year  is  im- 
ported into  the  United  States  from  Greenland,  its  only  important 
locality,  and  is  used  in  making  sodium  carbonate,  alum  and  calcium 
fluoride.  A  small  amount  of  cryolite  is  used  as  a  flux  in  the 
manufacture  of  aluminum  as  above  described. 

Abrasive  Materials. 

CORUNDUM  and  emery  were  produced  in  the  United  States  in 
1901  to  the  amount  of  4,257  f  tons.  About  8,000  tons  of  corun- 
dum and  emery  were  imported.  The  artificial  production  in  quantity 
of  an  extremely  hard  carbide  of  silicon,  known  as  carborundum,  is 
supplanting  these  natural  abrasives  to  the  extent  of  about  2,000 
tons  per  year. 

Gems. 

CORUNDUM  (the  varieties  ruby  and  sapphire),  TURQUOIS  and 
CHRYSOBERYL  are  all  found  of  sufficient  beauty  to  be  classed  as 
gems  or  precious  stones.  In  this  country  sapphires  have  been 

*  Engineering  and  Mining  Journal,  1899,  p.  8. 
^Mineral  Resources,  1902,  p.  886. 


346  DESCRIPTIVE   MINERALOGY. 

found  in  Montana,  but  their  status  in  the  gem  market  is  not  yet 
very  well  defined.  A  considerable  amount  of  turquois  of  a  mar- 
ketable grade  has  been  mined  in  New  Mexico  and  new  deposits 
are  reported  in  Nevada. 

CRYOLITE.— Eisstein. 

COMPOSITION. — AlNa3F6.     (Al  12.8,  Na  32.8,  F  54.4  per  cent.). 

GENERAL  DESCRIPTION. — Soft,  translucent,  snow-white  to  color- 
less masses,  resembling  spermaceti  or  white  wax  in  appearance. 
Occasionally  with  groups  of  triclinic  crystals  so  slightly  inclined 
as  to  closely  approach  cubes  and  cubic  octahedrons  in  angle  and 
form. 

Physical  Characters.     H,,  2.5.     Sp.  gr.,  2.95  to  3. 

LUSTRE,  vitreous  or  wax-like.      TRANSLUCENT  or  transparent. 

STREAK,  white.  TENACITY,  brittle. 

COLOR. — Colorless,  white,  brown. 

CLEAVAGE. — Basal  and  prismatic,  angles  near  90°. 

BEFORE  BLOWPIPE,  ETC. — Fuses  very  easily,  with  strong  yellow 
coloration  of  the  flame,  to  a  clear  globule,  opaque  when  cold. 
With  cobalt  solution,  becomes  deep  blue.  In  closed  tube,  yields 
acrid  fumes,  which  attack  and  etch  the  glass.  Soluble  in  acid 
without  effervescence. 

SIMILAR  SPECIES. — Characterized  by  its  easy  fusibility,  and 
fumes  which  attack  glass. 

REMARKS. — Found  at  Ivigtut,  Greenland,  as  a  large  bed  in  a  granite  vein,  and  con- 
tains,  scattered  through  it,  crystals  of  siderite,  quartz,  chalcopyrite  and  galenite.  This 
is  the  only  locality  where  cryolite  is  produced  in  commercial  quantities,  but  here  the 
supply  seems  inexhaustible.  Small  amounts  have  been  found  at  Miask,  Urals,  and  in 
the  United  States  at  Pike's  Peak,  Colorado. 

USES. — It  is  used  in  the  manufacture  of  sodium  carbonate,  and 
aluminum  hydroxide,  and  is  made  into  alum.  The  by-product,  cal- 
cium fluoride,  is  sold  to  smelters  and  glass  manufacturers.  Cryo- 
lite is  also  used  as  a  flux  or  bath  in  the  manufacture  of  aluminum. 

CORUNDUM.— Sapphire,  Ruby,  Emery. 

COMPOSITION. — A12O3,    (Al  52.9,  O  47.1  per  cent). 

GENERAL  DESCRIPTION. — With  the  exception  of  the  diamond, 
the  hardest  of  all  minerals.  Occurs  in  three  great  varieties,  which 
are  most  conveniently  described  separately. 


ALUMINUM  MINERALS. 


347 


Sapphire  or  Ruby. — Transparent  to  translucent,  sometimes  in 
crystals  and  of  fine  colors — blues,  reds,  greens,  yellows,  etc. 

Adamantine  Spar  or  Corundum. — Coarse  crystals  or  masses,  with 
nearly  rectangular  cleavage,  or  granular,  slightly  translucent,  and 
usually  in  some  blue,  gray,  brown  or  black  color. 

Emery. — Opaque,  granular  corundum,  intimately  mixed  with 
hematite  or  magnetite,  usually  dark-gray  or  black  in  color. 

FIG.  473. 


Corundum  Crystals,  Ceylon.     U.  S.  National  Museum. 

CRYSTALLIZATION.  —  Hexagonal.  Scalenohedral  class,  p.  42. 
Axis  c  =  1.363.  Crystals  often  rough  and  rounded.  Second 
order  pyramids  predominate  as  n,  o,  and  w  intersecting  the  vertical 


FIG.  474. 


FIG.  475. 


FIG.  476. 


348  DESCRIPTIVE  MINERALOGY. 

axis  at  respectively  %c,  %c  and  2c.     Unit  rhombohedron  p  and  the 
more  acute  form  /  (2c)  also  occur.     Supplement  angles  nn  =  51° 

58'  ;  00=  57°  38/  5  ww=  56°- 

Optically  — ,  with  rather  strong  refraction  but  weak  double  refrac- 
tion (a  =  1.759  ;  r  =  I-767)- 

Physical  Characters.     H.,  9.     Sp.  gr.,  3.95  to  4.11. 

LUSTRE,  vitreous  or  adamantine.     TRANSPARENT  to  opaque. 
STREAK,  white.  TENACITY,  brittle  to  tough. 

COLOR,  blue,  red,  green,  yellow,  black,  brown  or  white. 
CLEAVAGE,  rhombohedral,  angle  of  86°  4'. 

BEFORE  BLOWPIPE,  ETC. — Infusible  and  unaltered,  alone  or  with 
soda,  or  sometimes  improved  in  color.  Becomes  blue  with  cobalt 
solution  at  high  heat.  Insoluble  in  acids  and  only  slowly  soluble 
in  borax  or  salt  of  phosphorus. 

REMARKS. — Occurs  in  granular  limestone,  granite,  gneiss  and  other  crystalline  rocks 
and  in  the  gravel  of  river-beds.  It  is  usually  associated  with  chloritic  minerals,  rarely 
with  quartz,  and  is  frequently  found  altered,  and  many  alteration  products  occur,  as 
spinel,  feldspar,  mica,  tourmaline,  cyanite,  fibrolite,  etc.  The  American  localities 
producing  corundum  or  emery  are :  Raburn  County,  Ga. ;  Macon,  Clay  and  Jackson 
Counties,  N.  C. ;  Westchester  County,  N.  Y.  ;  Chester  County,  Pa.,  and  Chester,  Mass. 
Fair-sized  rubies  and  sapphires  have  been  obtained  near  Helena,  Montana,  and  at 
several  localities  in  North  Carolina.  The  finest  rubies  are  obtained  from  Upper 
Burmah  and  Ceylon. 

USES. — Sapphire  and  ruby,  when  clear  and  transparent,  are 
valuable  gems,  the  ruby  sometimes  being  more  highly  valued 
than  the  same  weight  of  diamond.  The  various  colors  have  dif- 
ferent names;  Blue,  sapphire;  red,  ruby;  yellow,  oriental  topaz; 
green,  oriental  emerald;  purple,  oriental  amethyst.  Adamantine 
spar  and  emery  are  the  most  important  abrasive  materials,  and 
thousands  of  tons  are  used  in  grinding  and  polishing  glass,  gems 
and  metals.  Corundum  can  be  used  in  the  electric  smelting 
processes  for  aluminum,  but  its  price  makes  this  unprofitable. 

BAUXITE. 

COMPOSITION.— A12O(OH)4,  with  usually  part  of  the  Al  replaced 
by  Fe. 

GENERAL  DESCRIPTION. — Disseminated,  rounded  grains,  oolitic 
and  sponge-like  to  clay-like  masses.  Also  fine-grained,  compact. 
Usually  white,  or,  if  ferruginous,  will  be  yellow,  brown  or  red. 


ALUMINUM  MINERALS.  349 

FIG.  477. 


Bauxite,  Bartow  County,  Ga.     U.  S.  National  Museum. 

Physical  Characters.     H.,  I  to  3.     Sp.  gr.,  2.4  to  2.5. 
LUSTRE,  dull  or  earthy.  OPAQUE. 

STREAK,  like  color.  TENACITY,  brittle. 

COLOR,  white,  red,  yellow,  brown  or  black. 

BEFORE  BLOWPIPE,  ETC.— Infusible.  Becomes  deep  blue  with 
cobalt  solution,  and  may  become  magnetic  in  reducing  flame.  In 
closed  tube  yields  water  at  high  heat.  Soluble  with  difficulty  in 
hydrochloric  acid. 

REMARKS. — Bauxite  may  have  been  deposited  from  solution  in  hot  alkaline  waters 
or  may  have  resulted  from  alteration  of  corundum.  It  is  usually  found  with  clay  or 
kaolin  associated  with  other  aluminum  minerals.  Large  deposits  exists  at  Beaux, 
France,  Lake  Wochein,  Carniola,  and  in  Antrim,  Ireland.  In  the  United  States  it  is 
mined  at  Floyd  county,  Ga.,  and  Bauxite,  Ark.  The  production  at  these  two  places  is 
extensive. 

USES. — Is  the  chief  source  of  aluminum,  and  is  also  used  in 
the  linings  of  basic  converters,  Siemens-Martin  furnaces,  etc.,  and 
in  the  manufacture  of  alum. 

DIASPORE. 

COMPOSITION.— AIO(OH),  (A12O3  85.1,  H2O  14.9  per  cent.). 

GENERAL  DESCRIPTION. — Thin,  flat,  orthorhombic  prisms,  foliated  masses  and  thin 
scales.  When  pure,  it  is  transparent  and  white  or  pinkish  in  color.  When  impure,  it 
is  often  brown 


350 


DESCRIPTIVE  MINER ALOG Y. 


PHYSICAL  CHARACTERS. — Transparent  to  nearly  opaque.  Lustre,  pearly  and  vitre- 
ous. Color,  gray,  white,  pink,  yellow,  brown.  Streak,  white.  H.,  6.5  to  7.  Sp.  gr., 
3.3  to  3.5.  Very  brittle.  Cleaves  into  plates. 

BEFORE  BLOWPIPE,  ETC. — Infusible.  Usually  decrepitates.  With  cobalt  solution, 
becomes  deep  blue.  In  closed  tube,  yields  water  at  high  heat.  Insoluble  in  acids. 

SIMILAR  SPECIES. — Distinguished  by  its  hardness,  cleavage  and  decrepitation. 

REMARKS. — Occurs  with  corundum  and  its  associates. 

GIBBSITE. 

COMPOSITION.— Al(OH),,  (A12O3  65.4,  H2O  34.6  per  cent). 
GENERAL  DESCRIPTION. — A  white  or  nearly  white  mineral,  usu- 

FIG.  478. 


Gibbsite,  Richmond,  Mass.     N.  Y.  State  Museum. 

ally  occurring  in  small  stalactites  or  thin  mamillary  crusts,  with 
smooth  surface  and  sometimes  fibrous  internal  structure.  Rarely 
in  small  six-sided  monoclinic  crystals.  When  breathed  upon,  it 
has  a  strong  clay-like  odor. 

Physical  Characters.     H.,  2.5  to  3.5.     Sp.  Gr  ,  2.38. 
LUSTRE,  faint  vitreous.  TRANSLUCENT. 

STREAK,  white.  TENACITY,  brittle  to  tough. 

COLOR,  white,  greenish,  reddish,  yellow.         CLEAVAGE,  basal. 


AL  UMINUM  MINERALS.  3  5  I 

BEFORE  BLOWPIPE,  ETC. — Infusible,  exfoliates,  glows  and  be- 
comes white.  With  cobalt  solution  becomes  deep  blue.  In 
closed  tube  yields  water.  Soluble  in  hydrochloric  or  sulphuric 
acid. 

REMARKS. — If  gibbsite  could  only  be  found  in  quantity  it  would  be  even  more  valu- 
able than  bauxite  for  the  manufacture  of  aluminum.  No  large  deposits,  however, 
are  known,  and  the  mineral  is  not  mined  except  when  it  occurs  in  comparatively  small 
quantity  with  the  bauxite  of  Georgia  and  Arkansas.  The  mineral  is  found  in  even 
smaller  quantity  at  Richmond  and  Lenox,  Mass.,  and  in  Dutchess  and  Orange  counties, 
N.  Y. 

ALUNOGEN. 

COMPOSITION.— A12(SO<)3  +  18  H2O,  (A12OS  15.3,  SO,  36.0,  H2O  48.7  per  cent.). 

GENERAL  DESCRIPTION. — A  delicate  fibrous  crust  of  white  or  yellow  color.  Some- 
times massive.  Tastes  like  alum. 

PHYSICAL  CHARACTERS.— Translucent.  Lustre,  vitreous  or  silky.  Color,  white 
yellowish  or  reddish.  Streak,  white.  H.,  1.5  to  2.  Sp.  gr.,  1.6  to  1.8.  Taste,  like 
alum. 

BEFORE  BLOWPIPE,  ETC.— Melts  in  its  own  water  of  crystallization,  but  becomes 
infusible.  It  is  colored  deep  blue  by  cobalt  solution.  In  closed  tube  yields  much 
acid  water.  Easily  soluble  in  water. 

REMARKS. — Formed  by  action  of  sulphuric  acid  of  decomposing  sulphides  upon 
aluminous  shales.  Also  formed  during  volcanic  action. 

ALUMINITE. 

COMPOSITION.  —  (A1O).,SO4.9H,O,  (A12O3  29.6,  SO,  23.3,  H,O  47.1  per  cent. ). 

GENERAL  DESCRIPTION. — Usually  found  in  white  rounded  or  irregular  masses  of 
chalk -like  texture  and  peculiar  harsh  feeling. 

PHYSICAL  CHARACTERS. — Opaque.  Lustre,  dull  or  earthy.  Color  and  streak,  white. 
H.,  I  to  2.  Sp.  gr.,  1.66.  Meagre  to  the  touch  and  adheres  to  the  tongue. 

BEFORE  BLOWPIPE,  ETC. — Infusible.  In  closed  tube  yields  much  acid  water. 
With  cobalt  solution  becomes  deep  blue.  Easily  soluble  in  acid. 

REMARKS. — Found  in  clay  beds.  Expense  of  transportation  alone  keeps  aluminite 
from  the  list  of  aluminium  ores.  Quite  extensive  deposits  occur  near  Silver  City,  New 
Mexico,  also  near  Trinidad,  Colo  ,  and  in  others  of  the  Western  States. 

ALUNITE.  —  Alum  Stone. 

COMPOSITION.  —  K(A1OH)3(SO4)2  +  3  H2O,  (A12O3  37.0,  K2O 
11.4,  SO3  38.6,  H2O  13  per  cent). 

GENERAL  DESCRIPTION. — Occurs  fibrous  and  in  tabular  to  nearly 
cubic  rhombohedral  crystals,  or  so  intermixed  with  a  siliceous 
material  as  to  form  a  hard  granular  and  nearly  white  rock. 

Physical  Characters.      H.,  3.5  to  4.     Sp.  gr.,  2.58  to  2.75. 
LUSTRE,  vitreous.  TRANSPARENT  to  nearly  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white,  grayish  or  reddish. 


352  DESCRIPTIVE  MINERALOGY, 

BEFORE  BLOWPIPE,  ETC. — Infusible  and  decrepitates.  With  cobalt 
solution  becomes  deep  blue.  With  soda  infusible,  but  the  mass 
will  stain  silver.  In  closed  tube  yields  water  at  a  red  heat.  Im- 
perfectly soluble  in  hydrochloric  or  sulphuric  acid. 

REMARKS. — Formed  by  action  of  sulphur  dioxide  and  steam  upon  trachyte  or  allied     \ 
rocks.     Occurs  at  Tolfa,  Italy,  in  Hungary  and  in  Rosita  Hills,  Colorado.     j-&l|jjlU    \> 

USES. — By  roasting  and  lixivation  with  water,  alum  is  obtained, 
and  the  Tolfa  rock  is  so  treated  for  manufacture  of  Roman  alum., 
The  rock  is  also  used  for  millstones. 

TURQUOIS. 

COMPOSITION. — A12(OH)3PO4'H2O  and  always  contains  some 
copper  which  gives  it  color. 

GENERAL  DESCRIPTION. — Sky  blue  to  green  opaque  nodules  or 
veins,  also  in  rolled  masses. 

Physical  Characters.     H.,  6.     Sp.  gr.,  2.6  to  2.83. 

LUSTRE,  dull  or  wax-like.         OPAQUE  or  slightly  translucent. 
STREAK,  white  or  pale  green.     TENACITY,  rather  brittle. 
COLOR,  sky-blue  to  apple-green. 

BEFORE  BLOWPIPE,  ETC. — Infusible,  becomes  brown  and  colors 
the  flame  green.  In  salt  of  phosphorus  yields  bead  greenish-blue 
when  cold,  which  on  charcoal  in  the  reducing  flame  becomes 
opaque  red.  Soluble  in  hydrochloric  acid,  the  solution  becoming 
fine  blue  with  ammonia.  In  a  nitric  acid  solution  of  ammonium 
molybdate  produces  a  yellow  precipitate  on  boiling. 

SIMILAR  SPECIES. — It  is  harder  than  chrysocolla. 

REMARKS. — Turquois  is  mined  in  the  United  States  at  Los  Cerrillos  in  New  Mexico, 
and  fine  material  is  obtained.  Also  in  Grant  county,  New  Mexico.  Previous  to  the 
opening  of  these  mines  turquois  had  been  obtained  almost  altogether  from  the  famous 
Persian  locality  and  from  Arabia.  The  mineral  is  also  known  to  occur  in  Arizona, 
California,  Colorado  and  Nevada. 

USES. — As  a  gem. 

WAVELLITE. 

COMPOSITION.— A16(OH)6(POJ4  +9H2O,  (A12O3  38.0,  P2O5  35.2, 
H2O  26.8  per  cent.).  F  is  sometimes  present. 

GENERAL  DESCRIPTION. — Hemispherical  masses  which,  when 
broken  yield  complete  or  partial  circles  with  radiating  crystals. 


ALUM IX I  ~M  MIXERALS. 


353 


rarely   large    enough  to    be    measured.     Occasionally  stalactitic. 
Color  most  frequently  white,  green  or  yellow. 

FIG.  479. 


Physical  Characters.     H.,  3.5  to  4.     Sp.  gr.,  2.31  to  2.34. 
LUSTRE,  vitreous.  TRANSLUCENT. 

STREAK,  white.  TENACITY,  brittle. 

COLQR,  colorless,  white,  yellow,  green,  brown,  blue,  black. 

BEFORE  BLOWPIPE,  ETC. — Whitens,  swells,  and  splits,  but  does 
not  fuse.  With  cobalt  solution  becomes  deep  blue.  In  closed 
tube  yields  acid  water.  Soluble  in  hydrochloric  acid.  Ammo- 
nium molybdate  produces  a  yellow  precipitate  from  nitric  acid  so- 
lutions. 

REMARKS. — In  the  United  States  is  most  abundant  at  Magnet  Cove,  Ark.,  West 
Whiteland,  Pa.,  and  Silver  Hill,  N.  C.  It  is  without  industrial  use. 


Lazulite.  —  (Mg.Fe.Ca)Al2(OH)2(PO4)2,  is  found  in  clay,  slate,  and  quartzite  as 
azure-blue,  acute,  monoclinic  pyramids  and  masses.     Usually  opaque. 


CHRYSOBERYL. 

COMPOSITION.  —  BeAl2O4,  (BeO  19.8,  A12O3  80.2  per  cent). 
GENERAL  DESCRIPTION.  —  Pale  green  or  yellowish  tabular  crys- 

FIG.  480.  FIG.  481. 


Urals. 


Haddam,  Conn. 


354  DESCRIPTIVE  MINERALOGY. 

tals;  thicker  deep  emerald -green  crystals,  which  by  transmitted 
light  are  a  purplish  red  ;  and  rolled  pebbles  like  green  bottle  glass, 
often  with  an  internal  opalescence.  Very  hard. 

CRYSTALLIZATION.  —  Orthorhombic  a  :  ~b  :  c  =  0.470  :  i  :  0.580. 
Often  flat  contact  twins  with  feather-like  striations,  Fig.  481. 
Alexandrite  occurs  in  simple,  Fig.  480,  or  twinned  crystals  showing 
unit  pyramid  /  and  prism  m  with  brachy -pyramid  ;-  =  (2(1  :  b  :  2r), 
{121}  ;  and  prism  n  =  (2d  \b\  CD  c),  {120}.  Supplement  angles 
are  mm  =50°  2\'  \  nn  =  86°  28'  ;  //  =  40°  f  ;  rr  =72°  17'. 

Optically  +.  Axial  plane  the  brachy -pinacoid.  Acute  bisec- 
trix vertical.  Pleochroic. 

Physical  Characters.     H.,  8.5.     Sp.  gr.,  3.5  to  3.84. 

LUSTRE,  vitreous  to  greasy.          TRANSLUCENT  to  transparent. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  pale  yellowish  green  to  emerald  green. 

BEFORE  BLOWPIPE,  ETC. — Infusible.  In  powder,  is  turned  blue 
by  cobalt  solution.  Insoluble  in  acids. 

VARIETIES. — Alexandrite,  the  deep  emerald-green  variety,  which 
is  columbine  red  by  transmitted  light. 

Cymophane  or  Cats  Eye. — Yellowish-green  and  opalescent. 

REMARKS.  —  No  fine  gems  have  been  found  in  the  United  States,  although  the  min- 
eral occurs  sparingly  in  Stowe,  Peru  and  Canton,  Me.,  New  York  City,  see  Fig.  189, 
and  Greenfield,  N.  Y.,  Haddam,  Conn.  The  best  gems  are  obtained  from  Ceylon,  the 
Ural  Mountains  and  Brazil. 

USES.  —  As  a  gem,  especially  the  alexandrite  and  cat's  eye. 


CHAPTER   XXXV. 

BORON,  SULPHUR,   TELLURIUM,  HYDROGEN  AND  CARBON 
MINERALS. 

THE   BORON   MINERALS. 

THE  minerals  described  are  : 


Acid 
Borates 

Sassolite 
Borax 
Ulexite 
Colemanite 
Boracite 

H3B03 
Na2B4O7,  ioH2O 
CaNaB6O8.8H,O 
Ca2B6Ou.5H20 

Monoclinic 
Monoclinic 

Monoclinic 
Isometric 

Boron  is  also  a  constituent  of  the  common  silicates  tourmaline 
and  datolite. 

Commercial  borax  is  manufactured  from  all  the  minerals  men- 
tioned, and  has  important  uses,  based  either  on  its  power  to  unite 
with  almost  any  oxide  to  form  a  fusible  compound,  or  upon  its 
antiseptic  or  detergent  properties.  It  is  used  in  welding,  as  basis 
of  enamels  on  metal  or  porcelain,  as  a  flux,  as  an  antiseptic  in  pack- 
ing meat,  in  antiseptic  powders  and  soaps,  and  in  washing,  dyeing, 
and  tanning. 

Sassolite,  to  the  extent  of  about  2  500  tons  yearly,  is  obtained  by 
condensing  and  evaporating  the  steam  issuing  from  fumaroles  in 
the  mountains  of  Tuscany.  About  8000  tons  of  pandermite  (cole- 
manite)  are  annually  obtained  in  Asia  Minor.  Boracite  is  from  the 
mines  at  Stassfurt,  Germany.  Large  deposits  of  calcium  borate 
occur  in  Chili,  Argentina  and  Bolivia  and  are  mined  to  the  extent 
of  some  17,000  tons  annually.  In  this  country  the  main  output 
is  from  the  colemanite  deposits  near  Daggett,  California,  although 
a  small  output  is  still  maintained  from  the  "marsh"  deposits  of 
borax  in  Nevada.  In  1902  borax  and  boric  acid  were  extracted 
to  the  extent  of  20,004  tons  in  California. 

When  the  crude  material  is  borax  with  other  sodium  and  cal- 
cium salts,  the  borax  is  extracted  by  boiling  in  hot  water,  cooling 
and  crystallizing.  The  calcium  borates  are  decomposed  by  sodium 

*  Mineral  Resources,  1902,  p.  892. 

355 


356  DESCRIPTIVE  MINERALOGY. 

carbonate  or  sulphate  to  form  borax,   or  by  sulphuric  or  hydro- 
chloric acid  if  boric  acid  is  first  to  be  produced. 

SASSOLITE.  -  Natural  Boracic  Acid. 

COMPOSITION.  —  H3BO3,  (B2O3  56.4,   H2C>43.6  per  cent). 

GENERAL  DESCRIPTION.  —  Small  white  or  yellowish  scales,  of 
pearly  lustre,  acid  taste,  and  somewhat  unctuous  feel.  Rarely 
stalactitic  or  in  minute  monoclinic  crystals.  Occurs  chiefly  in  solu- 
tion or  vapor  in  volcanic  regions. 

Physical  Characters.     H.,  i.  Sp.  gr.,  1.43. 

LUSTRE,  pearly.  TRANSLUCENT. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white  or  yellowish.  TASTE,  sour  or  acid. 

BEFORE  BLOWPIPE,  ETC. — Fuses  easily  with  intumescence  to  a 
clear  glass  without  color,  but  colors  the  flame  yellowish-green.  In 
closed  tube,  yields  water.  Soluble  in  water. 

REMARKS. — In  the  region  of  volcanoes  sassolite  is  brought  to  the  surface  in  the  jets 
of  steam,  collects  in  the  water  from  these  jets,  and,  to  some  extent,  forms  also  a  crust 
more  or  less  solid.  The  only  productive  locality  is  in  Tuscany.  It  also  forms  a  small 
proportion  of  the  boron  compounds  at  the  California  borax  localities. 

USES. — It  is  an  important  source  of  borax. 

BORAX.— Tinkal. 

COMPOSITION.— Na^O,.  i  oH2O,  (B2O3  36.6,  Na2O  16.2,  H2O 
47.2  per  cent.). 

GENERAL  DESCRIPTION. — A  glistening,  white  or  nearly  white 
efflorescence  or  constituent  of  certain  soils,  but  more  frequently 
in  solution  in  lakes,  or  as  well-formed  monoclinic  crystals  in  the 
mud  of  these  lakes.  The  crystals  closely  resemble  those  of  py- 
roxene in  form  and  angle. 

Physical  Characters.     H.,  2  to  2.5.     Sp.  gr.,  1.69  to  1.72. 
LUSTRE,  vitreous  to  dull.  TRANSLUCENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white,  gray,  bluish,  greenish.  TASTE,  alkaline. 

BEFORE  BLOWPIPE,  ETC. — Swells  greatly  and  fuses  to  a  clear 
glass.  Colors  flame  yellow,  and  if  mixed  to  a  paste  with  a  flux 
of  acid  potassium  sulphate  and  powdered  fluorite,  and  fused,  it  will 


BORON,    SULPHUR,    CARBON,    ETC.,    MINERALS.       357 

color  the  flame  bright  green.  In  closed  tube,  swells,  blackens, 
yields  much  water  and  a  burnt  odor.  Soluble  in  water.  If  treated 
with  a  few  drops  of  sulphuric  acid,  covered  with  alcohol,  and  the 
alcohol  set  on  fire,  a  green  flame  is  obtained. 

REMARKS.— Borax  in  the  United  States  is  produced  from  the  deposits  existing  in 
both  Nevada  and  California.  The  Nevada  localities  are  mainly  in  Esmeralda  County., 
while  those  of  California  are  in  Lake,  Bernardino  and  Inyo  Counties. 

USES.  In  welding,  soldering,  soap-making,  glass-making,  glaz- 
ing, as  a  flux  in  assaying,  refining  and  testing  metals,  as  a  preserva- 
tive, in  medicine,  and  as  chief  ingredient  of  many  washing  powders 
and  antiseptic  preparations. 

ULEXITE.— Boronatrocalcite. 

COMPOSITION.— CaNaB5O9.8H2O,  (B2O3  43.0,  CaO  13.8,  Na2O 
7-7,  H2O  35.5  per  cent.). 

GENERAL  DESCRIPTION. — White,  rounded  masses  (cotton-balls) 
of  loosely-compacted,  intertwined,  silky  fibres,  which  are  easily 
pulverized  between  the  fingers. 

Physical  Characters.     H.,  i.     Sp.  gr.,  1.65. 

LUSTRE,  silky.  TRANSLUCENT. 

COLOR  and  STREAK,  white.  TENACITY,  brittle. 

BEFORE  BLOWPIPE,  ETC. — Fuses  very  easily,  with  intumescence 
to  a  clear  glass.  Colors  flame  intense  yellow,  and  will  yield  green 
flame,  as  with  borax.  In  closed  tube  yields  water.  Soluble  in 
acids. 

REMARKS. — Occurs  in  dry  lakes  or  on  the  banks  surrounding  partially  dried  lakes, 
with  halite,  gypsum,  glauberite,  borax,  etc.  Is  probably  formed  by  the  action  of 
soluble  calcium  salts  on  boracic  acid  and  borax  in  solution  in  the  same  waters.  It  is 
abundant  in  Esmeralda  County,  Nevada,  and  is  also  found  in  several  of  the  California 
borax  localities  and  in  the  gypsum  beds  of  Nova  Scotia.  Large  deposits  also  occur 
in  the  dry  plains  at  the  north  of  Chili. 

USES. — It  is  a  source  of  part  of  the  borax  of  commerce. 

COLEMANITE.— Priceite,  Pandermite. 

COMPOSITION.  —  Ca2B6Ou  +  5H2O,  (B2O3  50.9,  CaO  27.2,  H,O 
21.9  per  cent). 

GENERAL  DESCRIPTION.  —  Occurs  in  groups  of  colorless  trans- 


358 


DESCRIPTIVE  MINERALOG  Y. 


parent  crystals  resembling  those  of  datolite  but  usually  larger,  and 
in  simpler  wedge-shaped  forms.      Also  found  in 
compact    white    masses    like    porcelain    and    in 
loosely  aggregated  chalk-like  masses. 

CRYSTALLIZATION.  —  Monoclinic.  Axes  a  :  ~b 
:  c  =  0.775  :  i  :  0.541  ;  fi  =  69°  51'.  Common 
faces  are  :  /  =  (20,  \  b  :  oo^r),  { 120}  ;  v  =  (a  :  b  :  "«  ". \-.:\i ---«•-- 
2c),  {221};  e  =  (coa  :  b  :  2c\  {021};  //  =  (a  :  oo 
b  :  2c),  {201}.  Usually  short  prismatic  and 
highly  modified.  Supplement  angles,  mm  =72° 

Physical  Characters.     H.,  4  to  4.5.     Sp.  gr.,  2.26  to  2.48. 
LUSTRE,  vitreous  to  dull.         TRANSPARENT  to  opaque. 
STREAK,  white.  TENACITY,  brittle. 

COLOR,  white  or  colorless.        CLEAVAGE,  parallel  clino-pinacoid 

Before  Blowpipe,  Etc.  —  Decrepitates,  exfoliates  and  fuses  imper- 
fectly, coloring  the  flame  green.  Insoluble  in  water,  easily  soluble 
in  hot  hydrochloric  acid  with  separation  of  boric  acid  on  cooling. 

VARIETIES. 

Priceite.  —  Loosely  compacted  white  chalky  masses. 
Pandermite.  —  Firm  compact  porcelain-like  white  masses. 

REMARKS.  —  Priceite  occurs  in  Curry  County,  Oregon,  in  layers  between  slate  and 
steatite.  Pandermite  is  found  in  a  bed  beneath  gypsum  near  Panderma  on  the  Sea  of 
Marmora.  Colemanite  at  Inyo  and  San  Bernardino  Counties,  Cal.,  with  celestite  and 
quartz.  Especially  abundant  near  Daggett  in  the  Mojave  Desert. 

USES.  —  Is  an  important  source  of  borax  and  yields  a  large  part 
of  the  American  output. 

BORACITE.  —  Stassfurtite. 


COMPOSITION.  —  Mg^LjB^Ogo  (B2O3  62.57,  MgO  31.28,  Cl  7.93  per  cent). 
GENERAL  DESCRIPTION. — Snow-white,  rather  soft  masses  (stassf urtite)  and  small 


FIG.  483. 


FIG.  484. 


BORON,    SULPHUR,    CARBON,    ETC.,    iMINERALS.       359 

hard  glassy  isometric  crystals  of  the  hextetrahedral  class,  p.  56,  usually  showing  the 
tetrahedron  p  with  or  without  the  cube  a  and  dodecahedron  d.  Strongly  pyroelectric. 

PHYSICAL  CHARACTERS.  —  Transparent  to  opaque.  Lustre,  vitreous.  Color,  white, 
yellowish,  greenish.  Streak,  white.  H.,  7  (crystals),  4.5  (masses).  Sp.  gr.,  2.9  to  3. 
Brittle. 

BEFORE  BLOWPIPE,  ETC.  —  Fuses  easily  with  intumescence,  to  a  white  glass  and 
colors  the  flame  yellowish  green.  In  closed  tube  yields  no  water  or  but  little.  Solu- 
ble slowly  in  hydrochloric  acid.  Strongly  heated  with  cobalt  solution  becomes  violet. 

REMARKS.  — Occurs  in  deposits  of  halite,  gypsum,  anhydrite,  and  especially  in  the 
immense  beds  of  potassium  and  magnesium  salts  at  Stassfurt,  Prussia. 


THE  SULPHUR  AND  TELLURIUM  MINERALS. 

The  minerals  described  are  : 

Elements  Sulphur  S  Orthorhombic 

Tellurium  Te  Hexagonal 

The  principal  sulphur  minerals,  however,  are  the  sulphides  and 
sulphates  elsewhere  described. 

According  to  the  estimate  of  J.  Struthers,*  the  United  States 
consumed  a  total  of  471,647  long  tons  of  sulphur  in  1902.  Of 
this  amount  177,480  tons  was  in  the  form  of  brimstone,  almost 
wholly  imported  from  Sicily,  and  294,167  tons  was  present  in  pyrite 
from  which  it  was  burned.  About  two-thirds  of  the  pyrite  was 
imported  and  mainly  from  the  Rio  Tinto  mines  of  Spain.  Sulphur 
is  also  recovered  in  large  quantities  from  the  former  waste  products 
of  gas  works,  Leblanc  soda  factories  and  other  chemical  works. 
Considerable  quantities  are  also  burned  off  from  the  sulphides  of 
zinc  and  copper  during  the  recovery  of  the  metals  and  in  a  few 
localities,  notably  in  Germany,  the  sulphur  dioxide  fumes  are  util- 
ized in  the  manufacture  of  sulphuric  acid. 

Nine-tenths  of  the  world's  supply  of  native  sulphur  is  obtained 
from  the  Island  of  Sicily.  In  this  country  12,054  long  tons  were 
produced  in  1903.! 

Sulphur  is  extracted  from  the  native  mineral  by  simple  fusion 
and  consequent  separation  from  the  gangue.  The  common  method 
in  use  in  Sicily  involves  the  burning  of  part  of  the  sulphur  to  melt 
the  remainder,  causing  heavy  loss  of  the  element.  The  crude  sul- 
phur may  be  refined  by  sublimation.  Pyrite  is  burned  directly  in 
specially  constructed  furnaces,  the  sulphur  dioxide  produced  being 
used  almost  solely  in  the  manufacture  of  sulphuric  acid. 

*  Mineral  Indttstry,  1902,  p.  579. 

^  Engineering  and  Mining  Journal,  1904,  p.  5. 


36° 


DESCRIPTIVE  MINERALOGY. 


TELLURIUM  is  included  in  this  section  on  account  of  its  close 
chemical  relation  to  sulphur.  It  has  no  commercial  importance, 
but  its  compounds  with  gold  and  silver  are  of  great  economic  im- 
portance. 

SULPHUR.  —  Brimstone. 

COMPOSITION.  —  S,  sometimes  with  traces  of  tellurium,  selenium, 
or  arsenic.  Often  mixed  with  clay  or  bitumen. 

GENERAL  DESCRIPTION. — Translucent  or  transparent,  resinous, 
crystals  of  characteristic  yellow  color.  Also  in  crusts,  stalactites, 
spherical  shapes,  and  powder.  Sometimes  brown  or  green. 


FIG.  485. 


FIG.  486. 


CRYSTALLIZATION. — Orthorhombic.  Axestf  \b  \c  =  0.813  :  i  : 
1.903.  Usually  the  pyramid/,  sometimes  modified  by  the  base  c, 
the  pyramid  s  =  (d  :  b  :  ^  r),  { 1 1 3 }  ;  or  the  dome  d  =  ( oo  a  :  7)  :  c), 
{on}.  Supplement  angles pp  =  73°  34'  ;  ss  =  53°  9';  cd=  62° 

17'. 

Optically  +  •     Axial  plane,  the  brachy-pinacoid.     Acute  bisec- 
trix vertical.     Axial  angle  with  yellow  light  2  V=  69°  5'. 
Physical  Characters.     H.,  1,5  to  2.5.     Sp.  gr.,  2.05  to  2.09. 

LUSTRE,  resinous.  TRANSPARENT  to  translucent. 

STREAK,  white  or  pale  yellow.      TENACITY,  brittle. 

COLOR,  yellow,  yellowish-orange,  brown,  or  gray, 

CLEAVAGE,  parallel  to  base,  prism  and  pyramid,  not  perfect. 

BEFORE  BLOWPIPE,  ETC. — Melts  easily,  then  takes  fire  and  burns 
with  a  blue  flame  aud  suffocating  odor  of  sulphur  dioxide.  In 
closed  tube  melts  and  yields  a  fusible  sublimate,  brown  hot,  yellow 
cold,  and  if  rubbed  on  a  moistened  silver  coin  the  coin  is  blackened. 
Insoluble  in  acids. 


BORON,    SULPHUR,    CARBON,    ETC.,    MINERALS.        361 

REMARKS.  —  Formed  in  large  deposits  by  the  decomposition  of  sulphides,  or  of  sul- 
phates, especially  gypsum,  which  by  water  and  decaying  organic  matter  are  reduced  to 
the  sulphide  with  subsequent  production  of  hydrogen  sulphide  which  on  decomposition 
forms  sulphur.  Sulphur  is  also  deposited  from  hot  springs. 

The  great  sulphur  producing  region  of  the  world  is  the  island  of  Sicily.  Deposits 
are  numerous  in  the  United  States,  and  are  worked  in  Calcasieu  Parish,  La.,  in  Beaver 
County,  Utah,  and  at  Rabbit  Hole  Springs,  Nevada.  Important  mines  are  operated  in 
Japan.  Extensive  deposits  are  also  known  in  California,  Wyoming  and  Texas.  Less 
important  occurrences  are  numerous. 

USES.  —  Sulphur  is  used  in  immense  quantities  for  the  manufac- 
ture of  sulphuric  acid,  gunpowder,  matches,  rubber  goods,  bleaching, 
medicines,  etc.  Large  quantities  of  it  are  recovered  in  various 
chemical  and  metallurgical  operations  as  by-products. 

TELLURIUM. 

COMPOSITION. — Te  with  a  little  Se,  S,  Au,  Ag,  etc. 

GENERAL  DESCRIPTION. — A  soft  tin  white  mineral  of  metallic  lustre  occurring  fine 
grained  or  in  minute  hexagonal  prisms. 

PHYSICAL  CHARACTERS. — Opaque.  Lustre,  metallic.  Color  and  streak,  tin-white. 
H.,  2  to  2.5.  Sp.  gr.,  6.1  to  6.3.  Rather  brittle. 

BEFORE  BLOWPIPE,  ETC. — On  charcoal  fuses  easily,  volatilizes,  coloring  flame 
green  and  forming  a  white  coat,  which  is  made  rose  color  by  transferring  to  porcelain 
and  moistening  with  sulphuric  acid.  Soluble  in  hydrochloric  acid. 

THE   HYDROGEN   MINERALS. 

HYDROGEN  is  a  constituent  of  many  minerals,  being  present  in 
combination  and  as  water  of  crystallization.  It  is  present  to  a 
limited  extent  in  natural  gas  and  in  volcanic  gases ;  it  escapes  in 
combination  with  sulphur  from  many  sulphur  springs  and,  in  com- 
bination with  carbon,  occurs  as  marsh  gas,  petroleum,  ozocerite,  etc. 
Its  compound  WATER  is  properly  included  as  a  mineral  and  has 
been  of  the  utmost  importance  in  mineral  formation  and  alteration 
(see  p.  197),  and  for  that  reason  is  considered  here.  The  uses  to 
which  water  is  put  are  so  numerous  and  well  known  that  they 
scarcely  need  mention.  In  1902  mineral  waters  to  the  extent  of 
64,859,451  gallons  were  sold  in  the  United  States.* 

WATER. — Ice,  Snow. 

COMPOSITION. — H2O,  (H.,  n.i,  O.,  88.9  per  cent.). 

GENERAL  DESCRIPTION.  —  Ice  or  snow  at  or  below  o°  C.  Water 
from  o°  to  100°  C.  Steam  above  100°  C.,  or  aqueous  vapor  at 
all  ordinary  temperatures. 


*  Mineral  Resources,  1902,  p.  993. 


362  DESCRIPTIVE  MINERALOGY. 

CRYSTALLIZATION. — Hexagonal.    Axis  c  =  1.403  approximately. 

As  snow,  the  crystals  are  principally  compound  star-like  forms 
branching  at  60°  and  of  great  diversity.  Simple  crystals  are 
sometimes  found  as  hail.  Optically  -f . 

FIG.  487.  FIG.  488.  FIG.  489.  FIG.  490. 


<;A 


Magnified  Snow  Crystals. 

Physical  Characters.     H.  (ice),  1.5.     Sp.  gr.  (ice),  0.91. 
LUSTRE,  vitreous.  TRANSPARENT. 

STREAK,  colorless.  TENACITY,  brittle. 

COLOR,  white  or  colorless,  pale  blue  in  thick  layers. 
Tasteless  if  pure. 

BEFORE  BLOWPIPE,  ETC. — Melts  at  o°  C.  Under  pressure  of 
760  mm.  boils  at  100°  C.  and  is  converted  into  steam. 

REMARKS. — Rarely  pure,  usually  containing  air,  carbon  dioxide,  some  of  the  salts 
of  calcium,  magnesium,  sodium,  potassium,  etc.,  and  even  traces  of  the  metals. 
When  pure  it  is  tasteless  and  a  universal  solvent. 

THE    CARBON    MINERALS. 

The  definite  minerals  described  are  : 

Elements  Diamond  C  Isometric 

Graphite  C  Hexagonal 

In  addition  to  these  there  are  a  large  number  of  gaseous,  liquid 
and  solid  carbon  compounds,  of  economic  importance  which  are 
on  the  border  line  of  mineralogy,  occurring  naturally  but  being 
generally  without  definite  composition  or  crystalline  form.  Among 
these  the  most  important  are  : 

NATURAL  GAS,  PETROLEUM,  ASPHALTS  AND  BITUMENS,  FOSSIL 
RESINS,  MINERAL  WAXES,  COAL. 

Carbon  also  exists  in  all  organic  matter,  in  all  carbonates ;  in 
the  carbon  dioxide  of  the  air ;  and  in  natural  gas. 

DIAMONDS  have  been  found  in  this  country,  but  practically,  the 
production  for  the  world  is  from  the  South  African  mines,  with  a 


BORON,    SULPHUR,    CARBON,    ETC.,    MINERALS.        363 

limited  amount  from  New  South  Wales  and  from  Brazil.  Nearly 
two  and  one-half  million  carats  were  mined  in  Kimberley,  South 
Africa,  in  1902.*  Extensive  new  deposits  have  been  discovered 
recently  near  Pretoria. 

GRAPHITE  is  mined  in  New  York,  Pennsylvania,  and  Rhode 
Island,  and  to  a  limited  extent  in  a  few  other  states.  In  1903  the 
output  of  crystalline  graphite  in  the  mines  of  this  country  was  2088 
tons.f  Amorphous  graphite  to  the  extent  of  4739  tons  was  also 
produced.  |  The  total  product  of  the  world  is  over  50,000  tons 
annually,  obtained  mainly  from  Ceylon  and  Austria.  The  uses  of 
graphite  are  numerous,  the  best  known  being  pencils,  crucibles, 
stove  polish,  lubricants,  paints  for  iron,  foundry  facings,  powder 
glazing,  electrotyping,  etc. 

NATURAL   GAS. 

Natural  gas  issues  from  the  earth  in  many  localities  but  mainly 
through  borings  or  wells  driven  to  control  its  outflow.  It  consists 
essentially  of  the  gas  methane,  more  commonly  known  as  marsh  gas, 
which  ordinarily  is  produced  when  organic  matter  decomposes 
under  water  or  out  of  contact  with  air.  It  also  contains  hydrogen, 
nitrogen  and  some  other  gases.  It  is  used  in  immense  quantities 
as  a  fuel  and,  after  being  enriched,  for  illuminating  purposes,  and  is 
also  burned  to  produce  lamp  black.  The  United  States  is  almost 
the  sole  commercial  producer  of  natural  gas.  In  1902  it  is  esti- 
mated that  more  than  two  hundred  billion  cubic  feet  were  pro- 
duced, valued  at  $30,867,668  §  and  replacing  more  than  ten  mil- 
lion tons  of  coal.  Pennsylvania,  Indiana,  West  Virginia  and  Ohio 
are  the  chief  producing  states. 

PETROLEUM. 

Petroleum  is  a  liquid  hydrocarbon  obtained  from  wells  or 
borings  in  the  regions  where  it  occurs.  It  varies  widely  in  its 
nature  and  composition  from  a  light  easily  flowing  liquid  to  thick 
viscous  oils  used  directly  for  lubricating  purposes.  It  is  usually 
of  a  dark  brown  or  greenish  color  and  has  a  distinct  fluorescence 
which  is  seen  not  only  in  the  crude  oil  but  also  in  most  of  the 
liquids  manufactured  from  it.  The  greater  part  of  the  American 

*  Mineral  Industry,  1902. 

f  Engineering  and  Mining  Journal,  1904,  p.  5. 

\  Mineral  Resources,  1902,  p.  977. 

§  Mineral  Resources  of  the  U.  S.,  1902,  p.  634. 


364  DESCRIPTIVE   MINERALOGY. 

output  consists  essentially  of  hydrocarbons  of  the  paraffine  series 
CnH2n+9  with  smaller  amounts  of  the  series  CnH2n  and  CnH2n_6. 
The  Russian  oil,  obtained  mainly  from  Baku,  on  the  Caspian,  is  dis- 
tinctly different  in  character,  consisting  mainly  of  the  naphthenes 
CnH2n  and  does  not  yield  nearly  so  much  illuminating  oil  on  dis- 
tillation. 

The  production  of  crude  petroleum  in  the  United  States  in 
1902  was  88,766,916  barrels;*  Ohio,  Texas,  California,  West 
Virginia,  Pennsylvania  and  Indiana  were  the  greatest  producers  and 
in  the  order  named.  Russia  produced  almost  as  great  an  amount 
but  of  a  much  less  value. 

Large  amounts  of  petroleum  are  used  in  the  crude  state  as  a 
fuel  and  a  smaller  amount  of  special  oils  for  lubricating  purposes. 
Its  chief  value  is  due  to  its  distillation  products,  mainly  kerosene. 
Other  valuable  products  arising  from  distillation  of  this  crude  oil 
are  gasoline,  naphtha,  benzene.  Various  products  such  as  lubri- 
cating oils,  vaseline  and  paraffine  are  made  from  the  residuum 
after  the  burning  oils  have  been  distilled  off. 
ASPHALTS  AND  BITUMENS. 

Under  this  head  may  be  included  the  true  ASPHALT  of  the  famous 
pitch  lakes  of  Trinidad  and  of  Bermudez,  Venezuela ;  the  MANJAK 
of  Barbadoes  ;  the  elastic  ELATERITE  of  Derbyshire,  England  ;  the 
ALBERTITE  of  New  Brunswick ;  the  GILSONITE  of  Utah,  etc.  Besides 
these  sandstone  and  limestone  impregnated  with  asphalt  occur  in 
Kentucky,  California,  Utah,  Texas,  Colorado,  Indian  Territory  and 
other  states  and  are  mined  and  ground  direct  for  pavements.  The 
above  names  designate  rather  indefinite  mixtures  of  hydrocarbons 
and  their  oxidized  products.  They  are  generally  black  in  color, 
have  a  pitch-like  lustre  and  burn  easily  with  a  pitchy  odor.  They 
vary  from  thick  highly  viscous  liquids  to  solids  and  are  slightly 
heavier  than  water. 

The  principal  use  is  for  street  pavements,  usually  mixed  with  70 
to  80  per  cent,  of  sharp  sand,  5  to  1 5  per  cent,  of  limestone,  and  a 
little  coal-tar  residuum.  They  are  also  used  as  cement,  roofing 
and  floor  material,  and  as  a  paint  for  coating  wood  or  metal  to 
prevent  decay  or  rust.  They  are  used  in  large  quantities  for  insu- 
lating electric  wires,  and  are  added  as  an  adulterant  and  coloring 
material  in  rubber  goods.  They  are  important  for  water  proofing 


*  Mineral  Resources  of  the  U.  S.,  1902,  p.  536. 


BORON,    SULPHUR,    CARBON,    ETC.,    MINERALS.        365 

purposes  both  on  wood  and  metal.      Manjak  and  Gilsonite  are  im- 
portant constituents  of  black  varnishes. 

The  residue  known  as  "malta"  resulting  from  the  distillation  of 
some  forms  of  petroleum  is  much  like  asphalt  in  its  characteristics 
and  composition  and  is  generally  included  in  trade  summaries.  The 
domestic  production  of  asphalt  and  asphaltic  rock  was  105,458  tons 
in  1902  and  146,883  tons  were  imported.* 

Fossil  Resins. 

The  fossil  resins  amber,  or  succinite,  copal  and  dammar  do  not 
occur  in  the  United  States.  They  are  oxidized  hydrocarbons  much 
resembling  ordinary  resin  in  appearance. 

AMBER,  or  succinite,  is  a  fossil  resin  found  chiefly  along  the 
Prussian  coast  of  the  Baltic  Sea.  It  is  usually  transparent  and  of 
a  yellowish  or  brownish  color.  Its  chief  use  is  for  jewelry 
and  for  mouth  pieces  of  pipes.  It  is  also  used  in  some  special 
varnishes. 

COPAL  is  dug  by  the  natives  from  the  soil  on  both  the  east  and 
west  coasts  of  Africa.  It  is  soluble  with  difficulty  in  alcohol  and 
turpentine  and  is  very  valuable  for  varnishes.  It  is  too  hard  to  be 
scratched  by  the  nail. 

DAMMAR  is  obtained  both  as  a  true  resin  exuding  from  trees 
and  as  a  fossil  gum.  It  is  derived  from  the  East  Indies,  the 
Moluccas  and  from  New  Zealand.  It  is  not  so  hard  as  copal  but 
is  harder  than  resin.  It  is  a  valuable  basic  constituent  of  varnishes. 
The  New  Zealand  dammar  is  almost  wholly  fossil. 

Mineral  Waxes. 

OZOCERITE  or  mineral  wax  is  essentially  a  paraffin,  colorless  to 
white  when  pure,  but  oftener  greenish  or  brown,  and  possessing 
all  the  properties  of  beeswax  except  its  stickiness.  It  is  found  in 
Galicia,  Moldavia,  and  Utah,  and  is  extensively  used.  In  the 
crude  state  it  serves  as  an  insulator  for  electric  wires.  By  distill- 
ing it  yields :  a  refined  product,  ceresine,  used  for  candles,  waxed 
paper  and  hydrofluoric  acid  bottles  ;  burning  oils  ;  paraffine  ;  a 
product  with  properties  and  appearance  of  vaseline  ;  and  a  black- 
residuum  which  in  combination  with  india  rubber  constitutes  the 
insulating  material  called  okonite. 

In  1902  over  4000  tons  were  mined  in  Hungary. 

*  Mineral  Resources  of  the  U.  S.,  1902,  p.  659. 


366 


DESCRIPTIl  'E  MINERAL OG  Y. 


Mineral  Coal. 

Mineral  coal,  excluding  peat  and  lignite  which  retain  the  woody 
structure,  is  compact  massive  material  produced  by  a  gradual 
alteration  of  organic  deposits  chiefly  vegetable.  Bituminous,  or 
soft  coal,  which  retains  a  large  amount  of  volatile  matter  readily 
converted  by  heat  into  gases,  was  mined  to  the  extent  of  283,406,- 
691  tons  in  this  countiy  in  1903.*  Anthracite,  or  hard  coal,  which 
contains  little  volatile  matter,  was  produced  during  the  same  year 
to  the  amount  of  73,390,000  tons.  Nearly  one-half  of  our  total 
output  of  coal  is  mined  in  Pennsylvania.  The  United  States  now 
produces  about  one-third  of  the  coal  of  the  world. 

DIAMOND. 

COMPOSITION.  —  C. 

GENERAL  DESCRIPTION.  — Transparent,  rounded,  isometric  crys- 
tals with  a  peculiar  adamantine  lustre  like  oiled  glass.  Usually 
colorless  or  yellow,  and  with  easy  octahedral  cleavage.  Also 
translucent,  rough,  rounded  crystalline  aggregates  and  opaque 

FIG   491. 


Diamond  in  Matrix,  De  Beer's  Mine,  Kimberley,  S.  A.     Tiffany  &  Co. 

crystalline  or  compact  masses  of  gray  to  black  color  and  no  dis- 
tinct cleavage.  Especially  characterized  by  a  hardness  exceeding 
that  of  any  other  known  substance. 

CRYSTALLIZATION.  —  Isometric.      Hextetrahedral   class,  p.   56. 
Octahedra,  often  showing  inverted  triangular  depressions,  see  Fig. 

*  Engineering  and  Mining  Journal,  1904,  p.  4. 
f  Ibid. 


BORON,    SULPHUR,     CARBON,    ETC.,    MINERALS.         367 

491,  and  hextetrahedral  modifying  faces  are  most  common,  while 
rounded  hexoctahedra  and,  more  rarely,  cubes  and  other  forms 
occur.  Frequently  twinned  parallel  to  the  octahedron.  Index 
of  refraction  for  yellow  light  2.4195. 

Physical  Characters.     H.,  10.     Sp.  gr.,  3.15  to  3.52. 

LUSTRE,  adamantine.  TRANSPARENT  to  opaque. 

STREAK,  colorless.  TENACITY,  brittle. 

COLOR,  colorless,  yellow,  rose,  green,  blue,  gray,  black. 
CLEAVAGE,  octahedral. 

BEFORE  BLOWPIPE,  ETC. — Is  slowly  consumed,  producing  its 
equivalent  of  carbon  dioxide.  In  powder  it  is  burned  by  ordinary 
blowpipe  flame.  Insoluble  in  acids. 

VARIETIES. — Carbonado  or  Black  Diamond. — Opaque,  dark-col- 
ored, and  without  cleavage.  Sp.  gr.,  3.15  to  3.29. 

Bort. — Translucent,  non-cleavable,  crystalline  aggregates,  often 
harder  than  the  crystals  and  more  tough.  Sp.  gr.,  3.499  to  3.503. 
The  name  bort  is  also  applied  to  fragments  of  crystals. 

REMARKS. — Origin  not  known.  The  diamond  is  found  in  alluvial  deposits  with 
other  minerals,  such  as  gold,  platinum,  zircon.  The  great  South  African  localities, 
however,  while  in  part  alluvial  or  "river  diggings,"  are  chiefly  confined  to  a  limited 
area  where  they  occur  enclosed  in  a  wall  of  carbonaceous  shale  surrounding  a  ser- 
pentine shale  core,  in  which  are  found  not  only  the  diamonds,  but  garnets,  zircon 
magnetite,  etc.  Diamonds  have  also  been  found  in  quartzose  conglomerates  and  with 
the  so-called  flexible  sandstone  "itacolumite." 

Although  diamonds  have  been  found  in  isolated  localities  in  the  southern  and  west- 
ern States  no  deposits,  not  even  of  an  alluvial  character,  have  been  discovered  in 
North  America.  By  far  the  largest  diamond  deposit  ever  found  occurs  at  Kimberley, 
South  Africa,  and  immense  quantities  are  mined  here  annually.  New  and  promising 
deposits  have  been  opened  recently  near  Pretoria,  Transvaal.  Alluvial  deposits  occur 
in  Brazil,  India,  the  Urals  and  Borneo. 

USES.  —  As  a  gem  when  transparent  and  without  flaw  ;  colorless 
stones  and  those  of  decided  tints  ranking  superior  to  yellow  or 
brownish  stones.  Smaller  stones,  especially  the  translucent  and 
opaque  sort,  are  used  in  diamond  drills,  saws,  and  other  cutting 
machinery,  on  account  of  their  great  abrasive  power.  The  dust  is 
also  used  in  polishing  other  diamonds. 


368  DESCRIPTIVE  MINERALOGY. 

GRAPHITE.  — Plumbago,  Black  Lead. 

COMPOSITION. — C.     Sometimes  with  iron,  sand,  clay,  etc. 

GENERAL  DESCRIPTION. — Disseminated  flakes  or  scaly  to  com- 
pact masses,  and  more  rarely  six-sided  plates.  Soft,  greasy  and 
cold  to  the  touch ;  black  to  very  dark  gray  in  color  and  usually 
metallic  in  lustre.  When  impure  it  is  apt  to  be  slaty  or  earthy. 

Physical  Characters.     H.,  i  to  2.     Sp.  gr.,  2.09  to  2.25. 
LUSTRE,  metallic  to  dull.  OPAQUE. 

STREAK,  dark-gray.  TENACITY,  scales  flexible, 

COLOR,  black  or  dark  gray.  slightly  sectile. 

CLEAVAGE,  basal,  cleaves  into  plates.       UNCTUOUS,  marks  paper. 

BEFORE  BLOWPIPE,  ETC. — Infusible,  but  is  gradually  burned. 
May  react,  if  impure,  for  water,  iron  and  sulphur.  Insoluble  in 
acids.  If  a  piece  of  graphite  is  brought  into  contact  with  a  piece 
of  zinc  in  a  solution  of  copper  sulphate,  it  is  quickly  copper-plated. 
Molybdenite  under  the  same  test  is  very  slowly  plated. 

SIMILAR  SPECIES. — Differs  from  molybdenite  in  darker  color, 
streak,  flame  test  and  salt  of  phosphorus  bead,  and  as  above  men- 
tioned. Micaceous  hematite  is  harder  and  has  a  red  streak. 

REMARKS. — Graphite  probably  results  from  alteration  of  embedded  organic  matter 
coal,  peat,  etc.,  by  heat,  destructive  distillation  and  pressure.  It  occurs  disseminated 
in  crystalline  limestones  and  granites  and  in  larger  irregular  masses.  Large  deposits 
exist  in  Ceylon,  Austria  and  Eastern  Siberia.  Almost  all  the  American  output  is 
obtained  at  Ticonderoga,  N.  Y.  Deposits  at  Southampton,  Pa.,  and  near  Raleigh, 
N.  C.,  have  also  produced  graphite  in  commercial  quantities. 

USES.— Graphite  is  used  for  refractory  vessels,  as  crucibles,  re- 
torts, stove  polish,  etc..  for  lead  pencils,  in  electroplating,  in  elec- 
trical supplies,  in  casting  moulds,  as  a  finish,  as  a  lubricant  for 
machinery,  as  a  paint  for  iron,  etc.,  for  coating  metals,  shot,  gun- 
powder, etc.  Artificial  graphite  of  excellent  quality  is  now  made 
at  Niagara  Falls  from  anthracite  coal  in  electric  furnaces. 


CHAPTER   XXXVI. 

SILICA  AND  THE  SILICATES. 

THE  minerals  composed  of  silica  alone  and  the  silicates  cannot 
conveniently  be  classified  upon  an  economic  basis,  and  we  have, 
therefore,  followed  practically  the  order  of  Dana's  "  System  of  Min- 
eralogy," Sixth  Edition,  believing  that — in  this  country,  at  least — 
most  collections  of  minerals  will  be  arranged  in  this  order  for 
many  years.  The  order  herein  followed  is : 

A. — SILICA. 

B. — ANHYDROUS  SILICATES  : 

I.  Disilicates  and  Polysilicates. 
II.  Metasilicates. 

III.  Orthosilicates. 

IV.  Subsilicates. 

C. — HYDROUS  SILICATES  : 

I.  Zeolite  Division. 
II.  Mica  Division. 

III.  Serpentine  and  Talc  Division. 

IV.  Kaolin  Division. 

D. — TITANO  SILICATES. 

ECONOMIC  DISCUSSION. 

Aside  from  the  occasional  occurrence  of  certain  silicates  in  spec- 
imens suitable  for  gems,  only  a  few  of  this  greatest  group  of 
common  minerals  are  of  economic  importance  as  distinct  minerals. 
The  great  stone  or  quarry  industry,*  however,  which  represents  in 
the  United  States  a  capital  of  over  $100,000,000,  and  produced  in 
1902  material  worth  in  the  rough  over  $64,000,000,  consists  in  the 
extraction  of  blocks  of  either  limestone  and  marble  or  of  silica  and 
silicates.  For  instance,  in  1902  the  values  of  materials  quarried  in 
this  country  were  : 

*The  facts  and  figures,  where  given  for  the  year  1902,  are  taken  from  Mineral  Re- 
sources of  the  U.  S.,  1902. 

24  369 


370  DESCRIPTIVE   MIXER  A  LOGY. 

Granite $18,257,944 

Sandstone 9,437,646 

Bluestone 1,164,481 

Slate 5,696,051 

The  amount  of  stone  used  in  building  in  this  country  in  1902 
was  approximately  of  the  value  of  $21,000,000. 

GRANITE,  commercially  speaking,  includes  a  number  of  hard, 
durable  rocks,  such  as  granite  proper,  syenite,  gneiss,  basalt,  dio- 
rite,  and  andesite,  which  are  composed  of  silicates  —  usually  three 
or  more  —  and  principally  quartz,  the  feldspars  and  the  micas, 
pyroxene  and  amphibole.  It  is  used  in  enormous  quantities  in 
buildings,  in  paving  blocks  and  in  construction  of  bridges  and 
dams.  In  1902,  granite  to  the  value  of  $18,257,944  was  quarried 
in  the  United  States,  of  which  $5,660,129  worth  was  used  in  build- 
ing and  the  balance  in  paving  blocks,  monumental  work,  flagstones 
and  curbstones,  crushed  stone,  etc. 

SANDSTONE  is  composed  of  grains,  chiefly  quartz,  with  sometimes 
a  little  feldspar,  mica  or  other  minerals,  and  is  classified  as  siliceous, 
ferruginous,  calcareous  or  argillaceous,  according  to  the  nature  of 
the  cement  which  binds  the  grains  together.  Its  uses  are  the  same 
as  those  of  granite,  but  a  larger  proportion  of  the  quantity  quarried 
is  used  in  building.  In  1902,  sandstone  to  the  value  of  $9,437,646 
was  quarried  in  the  United  States. 

BLUESTONE  is  a  very  hard,  durable,  fine-grained  sandstone,  ce- 
mented together  with  siliceous  material.  It  is  used  principally  for 
flag  and  curb  stone.  In  1902,  bluestone  to  the  value  of  $1,164,- 
481  was  quarried  in  the  United  States. 

SLATE  is  used  chiefly  as  roofing  material  and  for  interior  work, 
such  as  blackboards,  table  tops,  sinks,  etc.  Slate  and  slate  manu- 
factures to  the  amount  of  $5,696,05 1,  were  produced  in  the  United 
States  in  1902,  and  4,071  tons  of  slate  and  shale  were  ground  for 
mineral  paint. 

FIBROUS  TALC  and  compact  talc,  or  soapstone,  are  extensively 
used,  the  former  for  grinding  to  "mineral  pulp,"  used  in  paper 
manufacture,  the  latter  for  many  purposes,  usually  because  it  is 
refractory,  expands  and  contracts  very  little,  retains  heat  well  and  is 
not  attacked  by  acids.  These  properties  make  it  valuable  in  fur- 
naces, crucibles,  sinks,  baths,  hearths,  electrical  switch  boards  and 
cooking  utensils.  Talc  is  also  used  in  cosmetics,  refractory  paints, 
slate  pencils,  crayons,  gas  tips,  as  a  lubricant  and  in  soap  making. 


SILICA    AND    THE   SILICATES.  371 

In  1902  there  were  produced  in  this  country  71,100  tons  of 
fibrous  talc  and  26,854  tonsof  soapstone. 

THE  MICAS,  muscovite,  phlogopite  and  biotite,  have  become  of 
great  importance  as  non-conductors  in  electrical  apparatus,  and 
are  also  used  in  stove  and  furnace  doors.  The  larger  sheets  are 
cut  and  split  to  the  desired  size  ;  the  waste  is,  to  some  extent,  built 
up  into  plates  suitable  for  certain  grades  of  electrical  work,  and 
for  covering  steam  boilers  and  pipes.  Large  amounts  of  formerly 
wasted  material  are  now  ground  and  used  for  decorative  interior 
work,  to  ornament  porcelain  and  glassware,  to  spangle  wall  paper, 
in  calico  printing,  as  a  lubricant  and  more  recently  as  an  absorbent 
of  nitro-glycerine  and  in  the  manufacture  of  certain  smokeless 
powders. 

Sheet  mica  to  the  amount  of  373,266  pounds  was  produced  in 
this  country  in  1902  and  1,400  tons  of  scrap  mica  were  ground. 

ASBESTOS.  —  The  minerals  amphibole  and  serpentine,  in  their 
fibrous  varieties,  are  known  commercially  as  asbestos,  and  are  ex- 
tensively used  as  incombustible  paper,  cloth,  cement,  boiler  and 
steam-pipe  covering,  yarn  or  rope  for  packing  valves.  Only  1,005 
tons  were  obtained  in  1902  in  the  United  States.  The  large  supply 
coming  from  Canada  and  Italy  is  the  fibrous  serpentine,  chrysotile. 

SERPENTINE  is,  to  some  extent,  mined  and  used  as  an  ornamen- 
tal stone,  but  is  commercially  classed  with  the  marbles. 

FELDSPAR  is  crushed  in  large  quantities  for  admixture  with 
kaolin  in  the  manufacture  of  porcelain.  In  the  United  States 
45,287  tons  were  produced  in  1902. 

QUARTZ  is  used  in  large  amounts  in  the  manufacture  of  sand- 
paper, porcelain,  glass,  honestones,  oilstones,  and  as  a  flux.  Its 
colored  and  chalcedonic  varieties  are  used  as  semi-precious  or 
ornamental  stones.  In  1902  the  United  States  produced  over 
i  ,000,000  long  tons  of  quartz  and  quartz  sand.  Ground  flint,  which 
is  included  under  this  head,  is  used  as  a  scouring  powder  in  soaps 
as  well  as  for  the  other  purposes  mentioned. 

INFUSORIAL  EARTH  is  .calcined  and  made  into  water  filters,  pol- 
ishing powders,  soap  filling  and  boiler  and  steam-pipe  covering. 

KAOLIXITE  AND  CLAY.  —  Enormous  and  varied  industries  use  as 
their  raw  material  the  beds  of  clay  which  result  from  the  decom- 
position of  the  feldspars  and  other  silicates.  These  beds  are  com- 
posed in  part  of  some  hydrous  aluminum  silicate  such  as  kaolinite, 
but  usually  with  intermixed  quartz,  mica,  undecomposed  feldspar, 


372 


DESCRIPTIVE  MINERALOGY. 


oxides  and  sulphides  of  iron.  Their  properties  and  uses  depend 
chiefly  upon  their  composition.  Brick,  tile  and  pottery  to  the 
amount  of  $122, 169,531  were  manufactured  in  1902  in  the  United 
States. 

The  clay  industries  include  the  manufacture  of  common  brick, 
paving  brick,  fire-brick,  and  hydraulic  cement,  all  varieties  of 
earthenware,  stoneware  and  porcelain,  terra  cotta,  sewer  pipes  and 
drain  tiles,  arid  are  carried  on  all  over  the  country  and  the  world. 

FULLERS  EARTH,  a  kind  of  clay,  was  mined  in  Florida  to  the  ex- 
tent of  11,492  tons  in  1902,  and  used  in  the  refining  and  clarifying 
of  mineral  oils.  Several  thousand  tons  are  imported  from  Eng- 
land for  bleaching  lard  and  cottonseed  oils. 

GARNETS  to  the  amount  of  3926  tons  were  ground  for  abrasives 
in  1902. 

GEMS.  —  The  minerals  beryl,  garnet,  topaz,  tourmaline,  spodu- 
mene,  titanite  and  chrysolite  are  sometimes  found  in  specimens 
which  are  valuable  as  gems. 


SILICA. 

The  minerals  composed  of  silica  (SiO2)  are  : 


Quartz 

Tridymite 
Opal 


Si02 
Si02 
Si02.«H20 


Hexagonal 
Hexagonal 


QUARTZ.  —  Agate,  Jasper,  Chalcedony. 

COMPOSITION.  —  SiO2,  (Si  46.7,  O  53.3  per  cent), 
GENERAL  DESCRIPTION. — A  hard,  brittle  mineral  which  is  best 
known  in  transparent,  glassy,  hexagonal  crystals,  and  as  the  some- 
FIG.  492.  FIG.  493.  FIG.  494. 


what  greasy  lustred,  shapeless,  transparent  mineral  of  granite  and 
other  igneous  rocks.  Crystals  frequently  occur  white,  ame- 
thyst, smoky  and  red.  Translucent,  wax-like,  non-crystalline 


SILICA   AND    THE  SILICATES. 


373 


layers  of  gray,  yellowish  and  bluish  tints  are  often  found  in  cavi- 
ties with  usually  a  mammillary  or  botryoidal  structure.  It  is  also 
found  as  nearly  opaque,  non -crystallized  material  containing  con- 


Smoky  Quartz.     N.  Y.  State  Museum. 

siderable  amounts  of  iron,  and  alumina,  and  often  highly  colored, 
as  red,  brown,  or  yellow. 

CRYSTALLIZATION.  —  Hexagonal.      Class  of  trigonal  trapezohe- 
dron,  p.  49.     Axis  r=  1.0999.     Usually  a  combination  of  unit 


FIG.  496. 


FIG.  497. 


FIG.  498. 


FIG.  499. 


prism  m  with  one  or  both  unit  rhombohedra,  /  and  ^,  the  former 
often  larger  and  brighter,  and  the  prism  faces  nearly  always  hori- 
zontally striated.  The  second  order  pyramid  s  =  (2a  :  2a  :  a  :  2c)  ; 
{ 1 1 2 1 } ;  frequently  occurs  and  rarely  the  trapezohedral  faces 


374  DESCRIPTIVE  MINERALOGY. 

x=  (^a  :  6a  :  a  :  6r),  {5161};  either  right,  Fig.  498,  or  left,  Fig. 
499.  Supplement  angles  pp  =  85°  46';  mp  =  38°  13';  ins  =37° 
58'  ;  mx=  12°  i'. 

Twinned  crystals  are  not  rare.      See  page  65. 

Optically  +.  With  low  refraction  and  weak  double  refraction 
(a  =  1.544;  f  =  1.553  f°r  yellow  light).  Circularly  polarizing. 
Basal  sections  I  mm.  thickness  turn  the  plane  of  polarization  for 
yellow  light  21.7°  to  right  or  left. 

Physical  Characters.     H.,  7.     Sp.  Gr.,  2.6  to  2.66. 

LUSTRE,  vitreous  to  greasy.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle  to  tough. 

COLOR,  colorless  and  all  colors. 
CLEAVAGE,  difficult,  parallel  to  rhombohedron. 

BEFORE  BLOWPIPE,  ETC. — Infusible.  With  soda,  fuses  with 
marked  effervescence  to  a  clear  or  opaque  bead,  according  to  the 
proportions  used.  Insoluble  in  salt  of  phosphorus  and  slowly 
soluble  in  borax.  Insoluble  in  all  acids  except  hydrofluoric. 

VARIETIES. 

A.  CRYSTALLINE  VARIETIES. — Vitreous  in  lustre,  often  transpa- 
rent ;  occurring  in  isolated  or  grouped  crystals  or  drusy  surfaces 
or  crystalline. 

Rock  Crystal. — Pure,  colorless  or  nearly  colorless  quartz. 

Amethyst. — Purple  to  violet  and  shading  to  white.  Fracture 
shows  lines  like  those  of  the  palm  of  the  hand.  Color  disappears 
on  heating,  and  is  probably  due  to  a  little  manganese. 

Rose  Quartz. — Light-pink  or  rose-red,  becoming  paler  on  long 
exposure  to  light.  Usually  massive.  Colored  by  titanium  or 
manganese. 

Yellow  Quartz  or  False  Topaz. — Light  yellow. 

Smoky  Quartz. — Dark  yellow  to  black.  Smoky  tint,  due  to 
some  carbon  compound. 

Milky  Quartz  or  Greasy  Quartz. — Translucent.  Usually  mass- 
ive. Common  as  a  rock  constituent. 

Ferruginous  Quartz. — Opaque,  brown  or  red  crystals,  sometimes 
small  and  cemented  like  a  sandstone. 

Aventurine. — Spangled  with  scales  of  mica,  hematite,  or  goethite. 

Cat's  Eye. — Opalescent,  grayish-brown  or  green  quartz  with  in- 
cluded parallel  fibres  of  asbestus. 


SILICA   AND    THE  SILICATES.  375 

B.  CHALCEDONIC  VARIETIES. — With  lustre  like  wax.     Translu- 
cent.    Not  in  crystals.     Frequently  nodular,  mammillary,  stalac- 
titic  or  filling  cavities. 

Chalcedony. — Pale  blue  or  gray  varieties,  uniform  in  tint. 

Agate. — Strata  or  bands  representing  successive  periods  of  depo- 
sition, and  frequently  of  different  tints  or  with  irregularly  mingled 
colors  or  visible  colored  inclusions  constituting  such  sub-varieties 
as  banded  agate,  clouded  agate,  moss  agate,  ruin  or  fortification  agate, 
etc. 

Carnelian  or  Sard. — Blood-red  or  brownish-red. 

Onyx  and  Sardonyx. — Parallel  layers  of  lighter  and  darker  color, 
as  white  and  black,  white  and  red,  etc.  The  layers  are  in  planes. 

Chrysoprase. — Apple-green. 

Prase. — Dull  leek-green. 

Plasma,  Heliotrope  and  Bloodstone.  Bright  to  dark-green, 
spotted  with  white  or  red  dots. 

C.  JASPER  VARIETIES. — Opaque,  dull  in  lustre,  usually  high  in 
color,  impure  from  clay  and  iron. 

FIG.  500.  FIG.  501. 


Herkimer  Co.,  N.  Y.  Agate.     Schlottwitz,  Saxony. 

D.  IN  ADDITION  TO  THESE,  there  are 

Flint. — Smoky-gray  to  nearly  black,  translucent  nodules,  found 
in  chalk-beds. 

Touchstone. — Velvet-black  and  opaque,  on  which  metal  streaks 
are  easily  made  and  compared. 

Sandstones. — Quartz  grains  cemented  by  silica,  iron  oxide,  clay, 
calcium  carbonate,  etc. 

Qtiartzite,  compact  quartz,  granular  or  slaty  in  structure. 

REMARKS. — Quartz  is  chiefly  found  as  an  original  constituent  of  such  rocks  as 
granite,  gneiss,  etc  ,  formed  by  igneous  or  plutonic  action,  and  also,  to  a  very  large 
extent,  as  a  deposit  from  solution  in  water.  Silicates  are  attacked  by  carbonated 


3?6  DESCRIPTIVE  MINERALOGY. 

wat  :rs,  forming  carbonates  of  calcium,  magnesium,  sodium,  etc.,  and  leaving  a  resi- 
due of  silica.  This,  in  turn,  is  soluble  in  hot  solutions  of  these  same  carbonates,  and 
is  dissolved,  transported,  and,  by  evaporation  and  cooling,  is  redeposited,  filling  seams, 
cavities,  veins,  etc.  Quartz  is  the  most  common  of  all  solid  minerals,  and  occurs  with 
almost  all  other  species  and  in  almost  all  localities. 

USES. — Aside  from  the  uses  of  the  quartz  rocks  in  building,  etc., 
large  quantities  of  quartz  are  used  in  the  manufacture  of  sand- 
paper, glass,  porcelain  and  as  an  acid  flux  in  smelting.  The  chal- 
cedonic  varieties — agate,  onyx,  etc. — are  often  polished  and  used 
as  ornaments,  and  so  also  are  some  of  the  jaspers.  Rock  crystal 
is  used  in  cheap  jewelry,  and  is  cut  for  spectacles  and  for  some 
forms  of  optical  apparatus.  The  colored  crystalline  varieties  are 
often  cut  in  cheap  jewelry,  and  the  amethyst,  when  of  a  particular 
dark  purple,  is  highly  valued  as  a  gem. 

TRIDYMITE. 

COMPOSITION.— SiO2. 

GENERAL  DESCRIPTION. — Small  colorless,  six  sided  plates.  Often  in  wedge-shaped 
groups  of  three  (trillings),  which  are  sometimes  octahedral  in  appearance. 

PHYSICAL  CHARACTERS. — Transparent.  Lustre,  vitreous.  Color,  colorless  or 
white.  Streak,  white.  H.,  7.  Sp.  gr.,  2.28  to  2.33.  Brittle. 

BEFORE  BLOWPIPE,  ETC. — Like  quartz,  but  soluble  in  boiling  sodium  carbonate. 

REMARKS. — Occurs  in  cavities  in  volcanic  rocks,  such  as  trachyte  or  andesyte. 

OPAL. 

COMPOSITION. — SiO2.«H2O,    (H2O,  5  to  12  percent.). 

GENERAL  DESCRIPTION. — Transparent  to  translucent  veins  and 
masses,  usually  of  milky-white  or  red  color  and  frequently  show- 
ing blue,  green,  red,  etc.,  internal  reflections  (opalescence).  This 
grades  into  less  translucent  and  opaque  masses,  with  no  play  of 
color  and  somewhat  resembling  chalcedony,  but  without  the  wax- 
like  lustre.  Other  varieties  are  transparent,  like  melted  glass,  and 
opaque  and  earthy. 

Physical  Characters.     H.,  5.5  to  6.5.     Sp.  gr.,  2.1  to  2.2. 
LUSTRE,  vitreous,  pearly,  dull.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

Color,  colorless  and  all  colors. 

BEFORE  BLOWPIPE,  ETC. — Infusible.  Becomes  opaque  and  yields 
more  or  less  water.  Soluble  in  hydrofluoric  acid  more  easily  than 
quartz  and  soluble  in  caustic  alkalies. 


SILICA   AND    THE  SILICATES.  377 

VARIETIES. 

Precious  Opal. — Milky-blue,  yellow  or  white  translucent  material 
with  fine  internal  reflections,  attributed  to  thin  curved  lamellae, 
which  have  been  cracked,  bent  and  broken  during  solidification. 

Fire  Opal. — Reddish  or  brown  in  color  and  with  reflections  hav- 
ing the  appearance  of  fire. 

Common  or  Semi-Opal. — Translucent  to  opaque,  with  greasy 
lustre  and  of  all  colors,  but  without  opalescence.  Most  frequently 
yellow  or  brown. 

Wood  Opal  — Petrified  wood,  the  petrifying  material  being  opal. 

Opal  Jasper. — Like  ordinary  jasper,  but  with  resinous  lustre. 

Hyalite. — Colorless  transparent  masses  resembling  drops  of 
melted  glass  or  of  gum  arabic. 

Geyserite,  Siliceous  Sinter. — Loose,  porous  rock  of  opal  silica 
deposited  from  hot  water.  Opaque,  brittle  and  often  in  stalactitic 
or  other  imitative  shapes. 

Fiorite  or  Pearl  Sinter. — Pearly,  translucent  material  found  in 
volcanic  tufa  and  near  hot  springs. 

Tripolite  or  Infusorial  Earth. — Massive,  chalk-like  or  clay- like 
material  composed  of  the  remains  of  diatoms. 

SIMILAR  SPECIES. — Softer  than  quartz  and  soluble  in  caustic 
alkalies.  May  also  yield  noticeable  water  in  a  closed  tube.  Rarely 
confused  with  any  other  mineral. 

REMARKS.— Occurs  in  fissures  in  igneous  rocks  or  imbedded  in  limestone,  clay- 
beds,  etc.  Fine  precious  opals  are  found  at  Gem  City,  Washington ;  at  Opaline, 
Idaho ;  also  in  Latah  County,  Idaho,  and  Morrow  County,  Washington.  Queretaro 
and  Zimapan,  Mexico,  also  yield  good  gems.  Other  famous  localities  are  Czerwe- 
nitza,  Hungary ;  Bula  Creek,  Queensland,  and  Wilcannia,  New  South  Wales.  De- 
posits of  infusorial  earth  occur  at  Dunkirk,  Md. ;  Richmond,  Va. ;  Virginia  City, 
Mo.,  also  in  Connecticut,  New  Hampshire,  New  Jersey  and  California.  All  of  these 
deposits  have  been  worked,  but  not  continuously. 

USES. — Precious  and  fire  opals  are  beautiful  gems.  Opalized 
wood  is  cut  and  polished  for  ornament.  Tripolite  has  many  uses ; 
e.g.,  polishing  and  washing  powders,  lagging  for  boilers,  cement, 
soluble  glass,  and  as  the  dope  in  dynamite. 

POLYSILICATES. 

The  POLYSILICATES  may  be  derivatives  of  H2Si2O8,  H6Si2O7, 
H4Si3O8,  and  possibly  other  more  complicated  silicic  acids,  or 
they  may  be  formed  by  isomorphic  mixtures  of  salts  of  these 


378  DESCRIPTIVE  MINERALOGY. 

acids  with  each  other  or  with  the  orthosilicates  or  metasilicates. 
Many  of  the  polysilicates  are  so  variable  and  so  complex  that  it 
is  impossible  to  express  their  composition  by  formula,  and  many 
others  are  designated  by  formulae  which  are,  at  the  best,  but  ap- 
proximations. Under  this  head  comes  Petalite,  a  derivative  of 
H2Si2O5,  and  the  important  subdivision  of  the  FELDSPARS,  deriva- 
tives of  H4SisO8  and  of  fairly  definite  composition. 

PETALITE. 

COMPOSITION.— LiAl(Si2O5)2. 

GENERAL  DESCRIPTION. — Glassy  white  or  gray  foliated  and  cleavable  masses  and 
rarely  minute,  colorless  crystals,  like  pyroxene  in  form. 

PHYSICAL  CHARACTERS. — Transparent  to  translucent.  Lustre,  vitreous.  Color, 
colorless,  white,  gray,  occasionally  pink.  Streak,  white.  H.,  6  to  6.5.  Sp.  gr.,  2.39 
to  2.46. 

BEFORE  BLOWPIPE,  ETC. — Phosphoresces  with  gentle  heat;  with  strong  heat, 
whitens  and  fuses  on  the  edges  and  colors  the  flame  carmine.  Insoluble  in  acids. 

THE  FELDSPARS. 

These  are  of  great  importance  as  rock-forming  minerals  and 
have  a  close  resemblance  in  many  characters ;  e.g.  : 

Very  similar  in  crystalline  form.  System  either  monoclinic  or 
triclinic.  Prism  angles  nearly  1 20° ;  many  of  the  other  angles 
closely  agreeing. 

Two  prominent  cleavages  inclined  at  or  near  90°. 

Hardness,  6  to  6.5. 

Specific  gravity,  generally  between  2.55  and  2.75. 

Composition,  R'AlSi3O8  or  R"Al2Si2O8,  or  isomorphic  mixtures 
of  these. 

The  feldspars  here  described  are : 

Orthoclase  KAlSi3O8  Monoclinic 

Microcline  KAlSi3O8  Triclinic 

Plagioclase  w(NaAlSi3O8)  +  «(CaAl2Si2O8)  Triclinic 

ORTHOCLASE.— Feldspar,  Potash  Feldspar. 

COMPOSITION.— KAlSi3O8,  with  some  replacement  by  Na. 

GENERAL  DESCRIPTION. — Cleavable  masses,  showing  angle  of  90; 
and  monoclinic  crystals,  of  flesh-red,  yellow  or  white  color.  Also 
compact,  non-cleavabie  masses,  resembling  jasper  or  flint.  Some- 
times colorless  grains  or  crystals. 

CRYSTALLIZATION.  —  Monoclinic.  Axes  /9  =  63°  57';  a\b \c 
=  0.659  :  i  10.555.  Most  frequent  forms:  unit  prism  m,  pina- 


SILICA   AND    THE  SILICATES. 


379 


coids  b  and  c  and  positive  orthodomes  o  =  (a  :  oo  b  :  c}  ;   (Toi); 
and  y  =  (a  :  oo  b  :  2c)  ;     {201  }.        Supplement  angles    are  :  mm 


61°  13'  ;  cm=  67°  47'  ;  co=  50°  i 


80°  18'. 


Twin  forms  of  Carlsbad  type,  Fig.  506,  twin  plane  the  ortho 
pinacoid,  are  very  common  ;  the  Baveno  type,  Fig.  507,  twin  plane 
a  clino  dome,  and  Mannebacher  type,  twin  plane  the  base  c,  Fig. 
508,  are  less  common. 


FIG.  502. 


FIG.  503.  . 


FIG.  504. 


FIG.  505. 


FIG.  506. 


FIG.  507. 


FIG.  508. 


Optically  — ,  with  weak  refraction  and  double  refraction.     Axial 
plane  usually  normal  to  b.     In  thin  sections  rarely  shows  multiple 
twinning  and  is  usually  turbid  from  kaolin. 
Physical  Characters.     H.,  6  to  6.5.     Sp.  gr.,  2.44  to  2.62. 

LUSTRE,  vitreous  or  pearly.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  flesh -red,  yellowish,  white,     CLEAVAGE,  parallel  to  c  and 
colorless,  gray,  green.  b,  hence  at  right  angles. 

BEFORE  BLOWPIPE,  ETC.  —  Fuses  in  thin  splinters  to  a  semi- 
transparent  glass  and  colors  the  flame  violet.  Insoluble  in  acids. 
VARIETIES. 

Ordinary.  —  Simple  or  twinned  crystals,  sometimes  of  great  size, 


DESCRIPTIVE  MINERALOGY. 


of  nearly  opaque  pale  red,  pale  yellow,  white  or  green  color. 
More  frequently  imperfectly  formed  crystals  and  cleavable  masses, 
in  the  granitic  rocks. 

Adularia.  —  Colorless  to  white,  transparent,  often  opalescent. 
Usually  in  crystals. 

Sanidine  and  Rhyacolite.  —  Glassy,  white  or  colorless  crystals  in 
lava,  trachyte,  etc. 

Loxoclase.  —  Grayish-white  or  yellowish  crystals,  which  have  a 
tendency  to  cleave  parallel  to  the  ortho  pinacoid. 

Felsite.  —  Jaspery  or  flint-like  masses  of  red  or  brown  color. 

SIMILAR  SPECIES.  —  Differs  from  the  other  feldspars  in  the  cleav- 
age at  90°,  the  greater  difficulty  of  fusion,  the  absence  of  stria- 
tions,  etc. 

REMARKS.  —  Usually  of  igneous  origin,  sometimes  secondary.  With  mica  and 
quartz  it  forms  the  important  rocks  granite,  gneiss,  and  mica  schist,  and  is  also  the 
basis  of  syenite,  trachyte,  porphyry,  etc.  It  changes  to  kaolin  quartz,  opal,  epidote  and 
muscovite,  by  the  removal  of  bases  through  the  action  of  acid  waters.  Orthoclase  is 
quarried  at  South  Glastonbury  and  Middletown,  Conn.  ;  Edgecomb  and  Brunswick, 
Me.  ;  Chester,  Mass.  ;  Brandywine  Summit,  Pa.  ;  Tarrytown  and  Fort  Ann,  N.  Y. 

USES.  —  It  is  one  of  the  constituents  of  porcelain  and  chinaware, 
chiefly  to  form  the  glaze,  but  partly  mixed  with  the  kaolin  and 
quartz  in  the  body  of  the  ware. 

MICROCLINE. 

COMPOSITION.  —  KAlSi3O8. 

GENERAL  DESCRIPTION.  —  Like  orthoclase,  except  that  the  macro  axis  is  at  89°  30' 
to  the  vertical  instead  of  90°,  and  the  basal  cleavage  often  shows  fine  striations.  In 
thin  basal  sections  between  crossed  nicols  it  shows  a  peculiar  interlaced  structure  due  to 
two  series  of  twin  lamellae  which  cross  nearly  at  right  angles  as  in  Fig.  5 10. 


FIG.  509. 


FIG.  510. 


Microcline,  Pike's  Peak,  Colorado, 
Foote  Mineral  Co. 


Microcline  Basal  Section  between 
Crossed  Nicols. 


SILICA   AND    THE  SILICATES.  381 

Optically  —  .  Axial  plane  nearly  normal  to  the  brachy-pinacoid.  The  extinction 
angle  on  a  basal  section  is  -f  15°  30' ',  while  that  of  orthoclase  is  o°. 

PHYSICAL  CHARACTERS.  — Essentially  as  in  orthoclase.  Sp.  gr.  2.54  to  2.57,  and 
cleavage  at  89°  30'  instead  of  90°. 

BEFORE  BLOWPIPE,  ETC.  —  As  for  orthoclase. 

REMARKS. — Includes  varieties,  amazon  stone,  perthite,  chesterlite,  etc.,  formerly 
grouped  under  orthoclase.  Often  interlaminated  with  albite  or  orthoclase. 


Anorthoclase.  — A  triclinic  sodium-potassium  feldspar  found  mainly  in  the  lavas  of 
Pantellaria.  Color,  lustre  and  hardness  the  same  as  for  other  feldspars.  Cleavage 
close  to  90°.  Sp.  gr.  2.59.  Distinguished  by  its  optical  characters. 

PLAGIOCLASE. — Albite,  Anorthite,  Oligoclase,  Labradorite. 

The  name  " plagioclase"  was  originally  given  to  minerals  closely 
resembling  common  feldspar  in  cleavage,  crystal  form,  mode  of 
occurrence,  hardness,  specific  gravity  and  other  physical  charac- 
ters, but  with  the  angle  between  the  two  cleavages  about  86°  in- 
stead of  90°.  The  very  great  variations  in  composition  led  to  the 
establishment  of  several  species,  in  which,  however,  the  variations 
in  composition  were  still  great,  and  finally  to  a  theory,  now  gen- 
erally accepted,  which  may  be  expressed  as  follows :  The  plagio- 
clases  consist  of  is  amorphous  mixtures  of  two  (or  three)  triclinic  com- 
pounds, NaA!Si308  and  CaAlzSizO&  (and  KAlSi^O^).  Some 
specimens  approach  the  end  members,  and  are  then  called  respec- 
tively albite,  anorthite  (and  microcline),  but,  in  general,  distinct  species 
cannot  be  said  to  ezist. 

In  accordance  with  this,  the  more  prominent  species  names  are 
here  given  as  varieties  of  the  group  name  PLAGIOCLASE. 

COMPOSITION.  —  ?«(NaAlSi3O8)  +  «(CaAl2Si2O8),  with  some  re- 
placement by  KAlSi3O8. 

GENERAL  DESCRIPTION.  —  Granular  masses  or  small  triclinic 
crystals,  or  coarser  masses.  Each  grain  or  crystal  cleaves  easily 
in  two  directions,  which  make  an  angle  of  about  86°  with  each 
other,  and  shows  on  one  or  both  surfaces  by  reflected  light  the 
parallel  "twin  striations."  Some  varieties  show  marked  play 
of  colors,  others  the  moonstone  effect.  Usually  light  colored, 
and  most  frequently  colorless,  white  or  faintly  tinged,  sometimes 
(labradorite)  dark  gray.  Just  about  the  hardness  of  a  good  knife. 

CRYSTALLIZATION. — Triclinic,  usually  in  crystals  resembling  that 
shown  in  Fig.  511,  with  supplement  angles  mM  approximately 
60°,  and  frequently  twinned  either  by  the  albite  law,  twin  plane 


382  DESCRIPTIVE  MINERALOGY. 

b,  Fig.  5  12,  which,  if  repeated,  results  in  striations  on  c\  or  by  the 
pericline  law,  twin  axis  the  macro  axis,  Fig.  513,  producing  stri- 
ations on  b. 

Albite  and  anorthite  are  frequently  crystallized,  the  other  varie- 
ties less  frequently. 

Optically  shows  weak  refraction  and  double  refraction.  Low 
order  gray  interference  colors.  Thin  sections  with  polarized  light 

FIG.  511.  FIG.  512.  FIG.  513. 


show  parallel  bands  due  to  the  twin  lamellae,  and  extinction  angles 
characteristic  of  the  variety. 

Physical  Characters.     H.,  5  to  7.     Sp.  gr.,  2.6  to  2.7. 

LUSTRE,  vitreous  or  pearly.  TRANSLUCENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  pure  white,  colorless  or  tinted  by  red  or  yellow.  Some- 
times dark  gray  or  green. 

CLEAVAGES,  at  angle  of  86°  approximately. 

BEFORE  BLOWPIPE,  ETC.  —  Fuses  with  difficulty  to  a  colorless 
glass  or  white  enamel,  and  usually  colors  the  flame  yellow.  In 
fine  powder,  is  either  slightly  decomposed  by  hydrochloric  acid  or 
is  insoluble. 

VARIETIES. 

Albite  (Soda  Feldspar,  Pericline).  —  NaAlSi3O8.  Usually  pure 
white,  often  granular  or  with  curved  cleavage  surfaces,  and  often 
in  crystals  (Figs.  5 1 1  to  5 1 3)  in  cavities  in  gneiss,  mica  schist  and 
granite  and  other  igneous  rocks,  especially  those  high  in  silica. 
Often  encloses  the  rarer  minerals,  tourmaline,  beryl,  chrysoberyl, 
topaz,  etc.  Is  the  chief  constituent  of  diorite.  Not  easily  altered. 

Anorthite  (Lime  Feldspar,  Indianite).  —  CaAl2Si2O8.  Compara- 
tively rare  as  a  pure  mineral.  Best  known  in  the  small  highly 
modified  glassy  crystals  of  Vesuvius  and  the  larger  white  crystals 


SILICA   AND    THE  SILICATES.  383 

of  Miyake,  Japan,  which  frequently  enclose  grains  of  green  chryso- 
lite and  are  often  covered  with  a  black  crust. 

Oligoclase  (Soda  Lime  Feldspar).  —  2  to  6  (NaAlSi3O8)  +  Ca- 
Al2Si2O8.  Not  rare,  accompanying  orthoclase  as  grayish  white, 
translucent  masses,  with  somewhat  greasy  lustre  and  marked  twin 
striations.  Occurs  also  as  reddish  cleavable  masses,  sunstone,  and 
rarely  as  crystals. 

Labradorite  (Lime  Soda  Feldspar).  —  NaAlSi3O8  +  I  to  3(Ca- 
Al2Si2O8).  Usually  dark  gray  cleavable  masses  often  associ- 
ated with  hypersthene.  Commonly  iridescent,  showing  beautiful 
changing  colors,  blue,  green  and  red,  from  inclusions  of  diallage, 
ilmenite  or  goethite.  Striated  like  oligoclase.  Occurs  in  the  gab- 
bros,  dolerites  and  other  basic  rocks ;  but  is  notably  absent  in 
localities  containing  orthoclase  and  quartz.  It  alters  readily  to 
zeolites,  calcite,  datolite,  etc.  Found  abundantly  in  the  Adiron- 
dacks,  N.  Y.,  in  the  Wichita  Mountains,  Ark.,  in  Quebec  and  in 
Labrador. 

Other  plagioclases  of  less  importance  are  :  Andesite,  NaAlSi3O8 
+  CaAl2Si,O8,  Bytawnite,  NaAlSi3O8  +  6(CaAl2Si2O8),  and  Oligo- 
dasc-Albite,  6(NaAlSi3O8)  +  CaAl2Si2O8. 

USES.  —  The  plagioclases  have  no  important  uses  except  as 
rock  constituents  and  the  limited  use  of  the  iridescent  varieties  for 
ornamental  work  (labradorite)  or  semi-precious  stones  (moonstone 
and  sunstone). 

THE    METASILICATES. 

The  METASILICATES  are  derivatives  of  H9SiO3,  and  the  most 
important  are  described  in  the  following  order  : 

Leucite  K.AHSiO,),  Isometric 

Orthorhombic 

Orthorhombic 

Monoclinic 

Monoclinic 

Monoclinic  ^  ^   j  - 

.'     ..  ..      ^/J" 

Monoclinic 
Hexagonal 
Triclinic 

IOLITE,  Mg3(AlFe)0(SiO4)4(SiO3)4f  Orthorhombic,  is  an  inter- 
mediate species  between  metasilicates  and  orthosilicates. 


Enstatite 
Hypersthene 
Pyroxene 
•Wollastonite 

'Pectolite 
Rhodonite 

PYROXENE  GROUP. 

(Mg.Fe)Si03 
(Mg.Fe)Si03 
(Ca.Mg.Mn.Fe.Al)SiO3 
CaSiO3 
HNaCa2(SiOs)s 
MnSiO 

£CZu2?i^ 

Amphibole 
Beryl 
Cyanite 

RSiOs 
BeAl2(Si08)6 
(A10)2Si03 

384  DESCRIPTIVE  MINERALOGY. 

Many  of  the  hydrous  silicates  are  also  derivatives  of  metasilicic 
acid. 

LEUCITE. 

COMPOSITION.— KAl(SiO3)2.  FlG- 

GENERAL  DESCRIPTION. — Gray,  translucent  to 
white  and  opaque,  disseminated  grains  and  trap- 
ezohedral  crystals  in  volcanic  rock. 

CRYSTALLIZATION. — Isometric  externally,  but 
with  polarized  light,  showing  double  refraction 
at  all  temperatures  below  500°  C. 

Physical  Characters.     H.,  5.5  to  6.     Sp.  gr.,  2.45  to  2.50. 
LUSTRE,  vitreous  to  greasy,  TRANSLUCENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white  or  gray,  or  with  yellowish  or  red  tint. 

BEFORE  BLOWPIPE,  ETC.  Infusible.  With  cobalt  solution,  be- 
comes blue.  Soluble  in  hydrochloric  acid,  leaving  a  fine  powder 
of  silica. 

REMARKS. — A  constituent  of  lavas,  sometimes  the  chief  constituent.  By  alteration, 
changes  to  kaolin,  mica,  nephelite,  orthoclase,  quartz,  etc.  It  is  not  common  in 
America,  but  is  found  in  the  Leucite  Hills,  Wyoming,  and  also  in  the  northwestern 
part  of  the  same  State.  Very  common  in  the  Vesuvian  lavas. 

USES. — Leucite  rock  has  long  been  used  for  millstones. 

ENSTATITE.— Bronzite. 

COMPOSITION.— (Mg.Fe)  SiO3. 

GENERAL  DESCRIPTION. — Brown  to  gray  or  green,  lamellar  or  fibrous  masses,  with 
sometimes  a  peculiar  metalloidal  lustre  (bronzite).  Rarely  in  columnar  orthorhombic 
crystals. 

PHYSICAL  CHARACTERS. — Translucent  to  opaque.  Lustre,  pearly,  silky  or  metal- 
loidal. Color,  brown,  green,  gray,  yellow.  Streak,  white.  H.,  5.5.  Sp.  gr.,  3.1  to  3.3. 
Brittle. 

BEFORE  BLOWPIPE,  ETC. — Fusible  on  the  edges.  Almost  insoluble  in  acids.  With 
cobalt  solution  is  turned  pink. 

REMARKS. — It  is  rare  in  quartzose  rocks,  but  occurs  frequently  in  meteorites  and 
with  chrysolitic,  basaltic  and  granular  eruptive  rocks.  Occurs  also  associated  with 
chondrodite,  apatite,  talc,  etc.  By  alteration  it  forms  serpentine,  talc,  and  limonite. 

HYPERSTHENE. 

COMPOSITION — (Mg.Fe)SiO3,  with  more  iron  than  enstatite. 

GENERAL  DESCRIPTION. — Dark-green  to  black,  foliated  masses  or  rare  orthorhom- 
bic crystals,  which  grade  into  enstatite.  Frequently  shows  a  peculiar  iridescence,  due 
to  minute  interspersed  crystals. 


SILICA   AND    THE  SILICATES. 


385 


PHYSICAL  CHARACTERS.— Translucent  to  opaque.     Lustre,  pearly  or  metalloidal. 
Color,  dark-green  to  black.     Streak,  gray.     H.,  5  to  6.     Sp.  gr.,  3.4  to  3.5.     Brittle. 

BEFORE   BLOWPIPE,  ETC. — Fuses  on  coal  to  a  black,  magnetic  mass.     Partially 
soluble  in  hydrochloric  acid. 

REMARKS. — Hypersthene  is  common  in  certain  granular  eruptive  rocks,  gabbros, 
norites,  etc. 

In  thin  sections   hypersthene  is  often  strongly  pleochroic  while  enstatite  is  only 
weakly  so.     Hypersthene  often  also  includes  tabular  brown  scales. 


BASTITE.  —  An  alteration  product  of  enstatite  near  serpentine  in  composition.  It  is 
usually  foliated  and  of  a  yellowish  or  greenish  color  and  has  a  peculiar  bronze-like 
lustre  on  the  cleavage  surface.  H.,  3.5-4.  Sp.  gr.,  2.5-2.7. 

PYROXENE.  —  Augite. 

COMPOSITION.— RSiO3.     R  =  Ca,  Mg,  Mn,  Fe,  Al,  chiefly. 

GENERAL  DESCRIPTION. — Monoclinic  crystals.  Usually  short 
and  thick,  with  square  or  nearly  square  cross-section,  or  octagonal 
and  with  well-developed  terminal  planes.  Granular,  foliated  and 
columnar  masses  and  rarely  fibrous.  Color,  white,  various  shades 
of  green,  rarely  bright  green,  and  black. 

CRYSTALLIZATION. — Monoclinic.  /9  =  74°  10'.  Axes  a  \~b  :  c 
=  1.092  :  i  :  0.589. 

FIG.  515.  FIG.  516.  FIG.  517.  FIG.  518. 


Diopside,  Diopside, 

Pitcairn,  N.  Y.         Rossie,  N.  Y.  De  Kalb,  N.  Y. 


FIG.  519. 


FIG.  520. 


Fassaite. 


FIG.  521. 


Leucaugite, 
Sing  Sing,  N.  Y. 
25 


Augite. 


Augite  twin. 


386  DESCRIPTIVE  MINERALOGY. 

Common  forms  :  unit  prism  m,  the  pinacoids  a,  b  and  c,  the 
negative  and,  more  rarely,  the  positive  unit  pyramids  p  and  p,  the 
negative  and  positive  pyramids  v  and  v  =  (a  :  b  :  2<r)  ;  {221}. 
Supplement  angles  are  :  mm  =  92°  50'  ;  pp  =  48°  29'  ;  //  = 
59°  n';J£  =  68°  42';  w=84°  12';  #=33°  49';  #  = 
42°- 2';  «/  =  49°  54';  ^=65°  21'. 

Contact  twins,  twinning  plane  a,  Fig.  521,  are  common.  Also 
twin  lamellae  parallel  c,  shown  by  striations  on  the  vertical  faces 
and  by  basal  parting.  Optically  -f.  Axial  plane  b.  Strong 
double  refraction.  Varying  axial  angle.  Usually  not  strongly 
pleochroic. 

Physical  Characters.     H.,  5  to  6.     Sp.  gr.,  3.2  to  3.6. 

LUSTRE,  vitreous,  dull  or  resinous.        OPAQUE  to  transparent. 
STREAK,  white  to  greenish.  TENACITY,  brittle. 

COLOR,  white,  green,  black,  brown. 
CLEAVAGE,  prismatic  (angle  87°  10'). 

BEFORE  BLOWPIPE,  ETC. — Variable.  Usually  fuses  easily  to 
dark  glass,  sometimes  to  magnetic  globule.  Not  generally  solu- 
ble in  acids. 

VARIETIES. 

Malacolite  or  Diopside. — CaMg(SiOs)2.  Usually  white  or  pale- 
green. 

Hedenbergite.— (Ca.Fe)(SiO3)2.     Grayish-green. 

Augite. — Chiefly  CaMg(SiO3)2,  but  containing  also  Al  and  Fe. 
Dark-green  to  black,  and  many  others  which  grade  into  each  other 
imperceptibly. 

Diallage. — Thin  foliated  pyroxene,  green  or  brown  in  color. 

SIMILAR  SPECIES. — Differs  from  amphibole,  as  therein  described. 

REMARKS. — Next  to  the  feldspars,  pyroxene  is  the  most  common  constituent  of 
igneous  rocks.  It  occurs  also  in  crystalline  limestones  and  dolomites,  and  usually  of 
some  light-green  or  white  color  (diopside).  In  serpentine  it  is  apt  to  be  lamellar 
diallage.  In  granite  it  is  usually  green,  and  in  eruptive  rocks  is  dark-green  or  black 
augite.  It  alters  to  chlorite,  serpentine,  amphibole,  etc. 


Acmite.  —  NaFe(SiO3)2  occurs  in  prismatic  or  needle  crystals  of  dark  green  or  dark 
brown  color.      It  is  strongly  pleochroic. 


Jadeite.  — NaAl(SiOs)2.      One  of  the  minerals  included  in  the  term  jade,  is  a  tough 
compact  translucent  material  of  dark  to  pale  green  color  found  in  Burma. 


SILICA   AND    THE  SILICATES.  387 

WOLLASTONITE. 

COMPOSITION.  —  CaSiO3. 

GENERAL  DESCRIPTION.  —  Cleavable  to  fibrous,  white  or  gray 
masses.  Also  in  monoclinic  crystals,  near  pyroxene  in  angle. 
Sometimes  compact.  Usually  intermixed  with  calcite. 

CRYSTALLIZATION.  —  Monoclinic.  Axes  a  \ 
Z  :  r  =  1.053  :  i  :  0.967  ;  /9  =  84°  30'.  FlG-  522- 

Common  forms  :  unit  prism  m,  unit  dome  o, 
pinacoids  a  and  c  and  prism  z  =  (a  :  | ~jb  :  co  c)  ; 
{320}.  Supplement  angles  are:  «mm=  92° 
42';  -3^=69°  54';  cd  =  40°  3'.  Optically-.  Harrisville,  N.  Y. 

Axial  plane  b. 

Physical  Characters.     H.,  4.5  to  5.     Sp.  gr.,  2.8  to  2.9. 
LUSTRE,  vitreous  to  silky.  TRANSLUCENT. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white,  gray,  or  light  tints  of  yellow,  red,  brown. 
CLEAVAGE. — O  and  i-~i  at  angle  of  84°  30'. 

BEFORE  BLOWPIPE,  ETC. — Fuses  with  difficulty,  coloring  the 
flame  red.  Soluble  in  hydrochloric  acid,  generally  effervescing 
and  always  gelatinizing. 

SIMILAR  SPECIES. — Differs  from  pectolite  and  natrolite  in  red 
flame,  difficulty  of  fusion,  and  absence  of  water.  Tremolite  does 
not  gelatinize. 

REMARKS. — Occurs  in  granular  limestone,  granite,  basalt,  lava,  etc.,  with  pyroxene, 
calcite,  garnet,  etc.  By  the  action  of  carbonated  or  sulphurated  waters  it  changes 
to  calcite  or  gypsum. 

PECTOLITE. 

COMPOSITION.  —  HNaCa2(SiO3)3. 

GENERAL  DESCRIPTION.  —  White  or  gray  radiating  needles  and  fibers  of  all  lengths 
up  to  one  yard.  Also  in  tough  compact  masses  and  rarely  in  monoclinic  crystals. 

PHYSICAL  CHARACTERS.  —  Translucent  to  opaque.  Lustre,  vitreous  or  silky. 
Color,  white  or  gray.  Streak,  white.  H.,  5.  Sp.  gr.,  2.68  to  2.78.  Brittle. 

BEFORE  BLOWPIPE,  ETC.  —  Fuses  easily  to  a  white  enamel  Yields  water  in 
closed  tube.  Gelatinizes  with  hydrochloric  acid. 

REMARKS.  —  Occurs  with  zeolites,  prehnite,  etc.,  in  cavities  and  seams  of  basic 
eruptive  rocks. 

RHODONITE. 

COMPOSITION.  —  MnSiO3,  with  replacement  by  Fe,  Zn  or  Ca. 
GENERAL    DESCRIPTION.  —  Brownish    red   to    bright    red,    fine 


DESCRIPTIVE  MINERALOGY. 
FIG.  523. 


Pectolite,  West  Paterson,  N.  J.     N.  Y.  State  Museum. 

grained    or  cleavable  masses  and  dissemi-  FlG-  5=4- 

nated    grains,  often    coated   with    a   black 

oxide.    Sometimes  in  triclinic  crystals  either 

tabular  parallel  to  c  or  like  the  forms  of 

pyroxene. 

CRYSTALLIZATION. — Fig.  524  shows  three 
pinacoids  a,  b  and  c,  the  hemi-unit  prisms 
in  and  M,  and  two  quarter  pyramids  v t  and 
,v  of  &  :  b  :  2c.  The  supplement  angles  are  Franklin  Furnace. 

mM=  92°  28'  ;  cm  =  68°  45'  ;  cM=  86°  23'. 

Physical  Characters.  H.,5.5  to 6.5.  Sp.  Gr.,  3.4  to  3.68. 
LUSTRE,  vitreous.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  brownish-red  to  flesh-red,  bright- red,  greenish, yellowish. 
CLEAVAGE,  prismatic,  angle  87°  38'  and  basal. 

BEFORE  BLOWPIPE,  ETC. — Blackens  and  fuses  easily  with  slight 
intumescence.  With  fluxes  reacts  for  manganese  and  zinc.  In 
powder  is  partially  dissolved  by  hydrochloric  acid,  leaving  a  white 
residue.  If  altered  may  effervesce  slightly  during  solution. 


SILICA   AND    THE  SILICATES. 


389 


SIMILAR  SPECIES. — Rhodochrosite  is  infusible,  dissolves  com- 
pletely with  effervescence  in  warm  acids.  Red  feldspars  are  less 
fusible,  and  do  not  give  manganese  reactions. 

REMARKS. — Occurs  with  iron-ore,  franklinite,  tetrahedrite,  etc.,  and  is  altered  by 
light,  air,  and  carbonated  waters  to  the  oxides  and  the  carbonates. 

AMPHIBOLE.  —  Hornblende. 

COMPOSITION.  —  RSiO3,  R  being  more  than  one  of  the  elements, 
Ca,  Mg,  Fe,  Al,  Na  and  K. 

GENERAL  DESCRIPTION.  —  Monoclinic  crystals  either  long  with 
acute  rhombic  section  or  shorter  with  six-sided  cross  section. 
Often  with  ends  like  flat  rhombohedron.  Also  columnar,  fibrous 
and  granular  masses,  rarely  lamellar,  often  radiated.  Colors  :  white, 
or  shades  of  green,  brown  and  black. 

FIG.  525.  FIG.  526.  FIG.  527. 


Russell,  N.  Y. 


CRYSTALLIZATION.  —  Monoclinic.  Axes  a  :  b  :  c  =  0.551  :  i  : 
0.294;  ,9=73°  58'. 

Common  forms  :  unit  prism  m,  pinacoids  b,  c  and  sometimes  a, 
unit  clino-dome  d  and  unit  pyramid  /.  Supplement  angles  are : 
w;/z=  5.5°  49' ;  r;«=75°52';  dd  =  31°  32'  ;  pp  =  31°  41'. 
Twinning  as  in  pyroxene. 

Optically  +  .     Axial  plane  b.     Strong  double  refraction.     Often 
strongly  pleochroic. 
Physical  Characters.     H.,  5  to  6.     Sp.  gr.,  2.9  to  3.4. 

LUSTRE,  vitreous  to  silky.  TRANSPARENT  to  opaque. 

STREAK,  white  or  greenish.  TENACITY,  brittle  to  tough. 

COLOR,  white,  gray,  green,  black,  brown,  yellow  and  red. 

CLEAVAGE,  prismatic,  angle  of  1 24°  1 1 '. 

BEFORE  BLOWPIPE,  ETC. — Varies.  Usually  fuses  easily  to  a 
colored  glass,  which  may  be  magnetic.  Not  affected  by  acids. 


39°  DESCRIPTIVE   MINERALOGY. 

VARIETIES  : 

Tremolite. — CaMg3(SiO3)4,  white  to  gray  in  color. 

Actinolite. — Ca(Mg.Fe)3(SiO3)4,  bright  green  or  grayish-green. 

Hornblende  and  Edenite. — Aluminous  varieties,  black  or  green 
in  color,  with  lustre  something  like  horn. 

All  of  these  occur  in  crystals  and  columnar  to  fibrous. 

Nephrite  or  Jade  is  compact  and  extremely  tough,  microscopi- 
cally fibrous,  may  have  composition  of  tremolite  or  actinolite. 

Asbestus  is  in  fine,  easily  separable  fibres,  white,  gray,  or  greenish. 

SIMILAR  SPECIES. — Differs  from  tourmaline  in  cleavage,  crystal 
line  form  and  tendency  to  separate  into  fibres.  The  differences 
between  it  and  pyroxene  are : 

Amphibole,  prism  angle  and  cleavage  124°;  tough,  often  fib- 
rous, rarely  lamellar,  often  blade-like  or  pseudo-hexagonal  crystals. 
Pyroxene,  prism  and  cleavage  angle  87° ;  brittle,  rarely  fibrous, 
often  lamellar  crystals,  square  or  octagonal. 

REMARKS. — Occurs  with  pyroxene,  serpentine,  talc,  magnetite,  quartz,  the  feld- 
spars, etc ,  and  forms  by  alteration,  epidote,  serpentine,  talc,  chlorite,  iron-ores,  etc. 

Much  of  the  material  passing  under  the  name  of  asbestus  is  fibrous  serpentine.  The 
best  of  the  pure  material  is  imported  from  Germany  and  Italy.  Producing  mines  in 
the  United  States  are  located  in  California,  Wyoming  and  Oregon.  North  Carolina, 
Georgia,  Pennsylvania  and  other  States  have  large  deposits,  but  the  quality  and  mode 
of  occurrence  do  not  allow  it  to  be  profitably  mined  at  present.  For  most  purposes 
the  fibrous  serpentine  of  Canada  is  superior  to  any  American  asbestus. 

USES.  —  Asbestos  is  made  into  cloth  and  boards,  which  are  in- 
combustible and  are  good  non-conductors  of  heat.  It  is  used  for 
roofing,  coverings  for  steam  pipes,  piston  packing,  theatre  curtains, 
firemen's  suits,  fire -proof  paints  and  cements,  and  for  lining  safes. 
It  is  made  into  yarns,  ropes  and  paper  for  fire -proof  purposes. 
Asbestos  of  long  fine  fiber  is  used  in  the  laboratory  as  a  filtering 
medium. 

Nephrite  or  jade  has  had  many  uses  in  prehistoric  and  more  re- 
cent times.  It  is  the  toughest  of  all  known  stones  and  in  the 
stone  age  was  used  for  weapons  and  tools.  In  China  and  India 
and  in  ancient  Mexico  it  was  carved  into  ornaments,  symbols  of 
authority  and  sacrificial  vessels,  etc.  It  was  supposed  to  be  a  cure 
for  kidney  diseases,  and  both  its  names  are  derived  from  words 
meaning  "  kidneys." 

Glaucophane. — A  sodium  amphibole,  NaAl(SiO3)2.FeMgSiO:j,  blue  in  color  and 
occurring  in  indistinct  prisms  or  in  columnar  and  fibrous  masses  especially  in  nietamor- 


SILICA   AND    THE  SILICATES. 


391 


phic  schists.      Crystals  show  distinctly  different  colors  when  viewed  by  transmitted  light 
through  different  faces.  ^^ 

Uralite.  —  An  amphibole  pseudomorphic  after  pyroxene,  having  the  crystal  form  of 
pyroxene  and  cleavage  of  amphibole. 


Crocidolite.  —  A  blue  to  green  fibrous  amphibole.  An  altered  South  African  form 
of  the  compact  mineral  which  has  a  peculiar  changeable  lustre  is  often  used  as  a  semi- 
precious stone  gem  under  the  name  of  "  tiger's  eye." 

BERYL.  —  Emerald,  Aquamarine. 

COMPOSITION.  —  Be3Al2(SiO3)6. 

GENERAL  DESCRIPTION.  —  Hexagonal  prisms,  from  mere  threads 
to  several  feet  in  length.  Usually  some  shade  of  green.  Some- 
times in  large  columnar  or  granular  masses.  Harder  than  quartz. 

FIG.  528.  FIG.  529.  FIG.  530. 


CRYSTALLIZATION.  —  Hexagonal.  Axis  c  =  0.499.  Usually  prism 
in  with  base  c,  sometimes  with  unit  pyramid  p  or  second  order 
form  e  =  (2 a  :  20.  :  a  :  2c) ;  {1121}.  Supplement  angles  cp  = 
29°  56';  ^  =  44°  56'. 

Optically  — .      Low  refraction  and  very  low  double  refraction 
(a=  1.5659;  f=  1-5703  for  yellow  light). 
Physical  Characters.     H.,  7.5  to  8.     Sp.  gr.,  2.63  to  2.8. 

LUSTRE,  vitreous.  TRANSPARENT  to  nearly  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  emerald  to  pale-green,  blue,  yellow,  white,  red,  colorless. 

CLEAVAGE,  imperfect  basal  and  prismatic. 

BEFORE  BLOWPIPE,  ETC.— Fuses  on  thin  edges,  often  becom. 
ing  white  and  translucent.  Slowly  dissolved  in  salt  of  phosphorus 
to  an  opalescent  bead.  Insoluble  in  acids. 

VARIETIES. 

Emerald.— Bright  emerald  green,  from  the  presence  of  a  little 
chromium. 


392  DESCRIPTIVE  MINERALOGY. 

Aquamarine. — Sky-blue  to  greenish-blue. 
Goshenite. — Colorless. 

SIMILAR  SPECIES. — Harder  than  apatite,  quartz  or  tourmaline. 
Differs  in  terminal  planes  from  quartz.  Lacks  distinct  cleavage 
of  topaz. 

REMARKS. — Occurs  in  granite,  mica-schist,  clay-slate,  etc.,  frequently  penetrating 
the  other  minerals,  showing  that  it  was  formed  before  them.  It  is  associated  with 
quartz,  micas,  feldspars,  garnet,  corundum,  zircon,  etc.  By  alteration  it  forms  kao- 
linite,  rriuscovite,  etc.  Beryls  are  especially  abundant  at  Ackworth  and  Grafton,  X.  H. ; 
Royalston,  Mass.;  Paris  and  Stoneham,  Me.;  Alexander  County,  X.  C. ;  the  Black 
Hills  of  South  Dakota,  and  Litchfield,  Conn.  .  Those  at  Ackworth  and  Grafton  are 
sometimes  of  immense  size.  One  crystal,  near  the  railroad  station  of  Grafton  Centre, 
measures  3  feet  4  inches  by  4  feet  3  inches  on  horizontal  section,  and  is  exposed  for 
over  5  feet.  Good  emeralds  have  been  obtained  in  this  country  from  Alexander 
County,  S.  C.,  and  especially  from  Stony  Point.  Aquamarines  and  other  gem  speci- 
mens have  been  obtained  at  Paris  and  Stoneham,  Me.;  Mount  Antero,  Colo.,  and 
several  places  in  North  Carolina.  Emeralds  of  finest  quality  are  obtained  near  Muso, 
United  States  of  Colombia,  also  from  India,  Brazil,  Siberia  and  Australia. 

USES. — Emerald  and  aquamarine  are  cut  as  gems. 

CYANITE.  —  Kyanite. 

COMPOSITION.  —  (AlO)2SiO3,  probably  a  basic  me- 
tasilicate.* 

GENERAL  DESCRIPTION.  —  Found    in    long    blade-  || 
like    triciinic    crystals,    rarely    with    terminal    planes.  |f — 7f 
The  color  is  a  blue,  deeper  along  the  center  of  the 
blades,  and  at  times  passes  into  green  or  white. 

Physical  Characters.     H.,  5  to  7.     Sp.  gr.,  3.56  to  3.67. 
LUSTRE,  vitreous.  TRANSLUCENT  to  transparent 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  blue,  white,  gray,  green  to  nearly  black. 
CLEAVAGE,  parallel  to  the  three  pinacoids. 

BEFORE  BLOWPIPE,  ETC. — Infusible,  with  cobalt  solution  be- 
comes blue.  Insoluble  in  acids. 

REMARKS. — Occurs  chiefly  in  gneiss  and  mica  schist,  and  appears  to  have  been 
formed  below  1300°,  as  at  this  temperature  it  is  changed  into  fibrolite.  It  is  associated 
with  pyrophyllite,  andalusite,  corundum,  etc.,  and  is  found  throughout  the  corundum 
regions  of  Massachusetts,  Pennsylvania,  North  Carolina,  and  Georgia. ' 

*Dana  places  cyanite  with  the  or thosil Scales  for  convenience. 


SILICA   AND    THE  SILICATES. 
FIG.  532. 


393 


Cyanite,  Pizzo  Forno,  St.  Gothard,  Switzerland.     Foote  Mineral  Co. 


394  DESCRIPTIVE  MINERALOGY. 

IOLITE.— Dichroite,  Cordierite. 

COMPOSITION.— Mg3(Al.Fe)6(SiO4)4(SiO3)4. 

GENERAL  DESCRIPTION.  —  Short,  six-  or  twelve-sided  orthorhombic  prisms  and 
massive,  glassy,  quartz-like  material.  Usually  blue  in  color.  The  color  is  often  deep 
blue  in  one  direction  and  gray  or  yellow  in  a  direction  at  right  angles  with  the  first. 

PHYSICAL  CHARACTERS. — Transparent  or  translucent.  Lustre,  vitreous.  Color, 
light  to  smoky  blue,  gray,  violet  or  yellow.  Dichroic.  Streak,  white.  H.,  7  to  7.5 
Sp.  gr.,  2.6  to  2.66.  Brittle.  Cleaves  parallel  to  brachy-pinacoid. 

BEFORE  BLOWPIPE,  ETC. — Fuses  with  difficulty,  becoming  opaque.  With  cobalt 
solution  becomes  blue-gray.  Partially  soluble  in  acids. 

REMARKS. — Occurs  in  gneiss  and  sometimes  in  granite,  rarely  in  volcanic  rocks,  and 
is  formed  by  contact  with  igneous  matter.  It  is  easily  altered  to  a  soft  lamellar  or 
fibrous  material  of  green  or  yellow  color,  and  is  rarely  found  entirely  unaltered. 

ORTHOSILICATES. 

The  ORTHOSILICATES  are  derivatives  of  H4SiO4,  as  Zircon,  ZrSiO4J 
Phenacite,  Gl2SiO4.  Isomorphic  mixtures  are  well  represented  by 
Biotite,  (H.K)2(Mg.Fe)Al2(SiO4)3;  acid  salts  by  Prehnite,  H2Ca2- 
Al2(SiO4)3,  and  basic  salts  by  Sillimanite,  Al(AlO)SiO4.  Haiiynite 
is  an  example  of  a  crystalline  mixture  of  an  orthosilicate  and  a  sul- 
phate. As  a  rule,  the  orthosilicates  are  less  stable  than  the  meta- 
silicates. 

The  orthosilicates  here  described  in  detail  are  : 

Nephelite  7NaAlSiO4  -j-  NaAl(SiO3)3  Hexagonal 

Lazurite  Complex  Isometric 

Garnet  R3"R/"(SiO4)s  Isometric 

Chrysolite  (Mg.Fe)SiOi  Orthorhombic 

Phenacite  Be2SiO4  ^  Rhombohedral 

Wernerite  Complex  Tetragonal 

Vesuvianite  Ca6Al(OH.F)Al2(SiO4)6  Tetragonal 

Zircon  ZrSiO4  Tetragonal 

Topaz  Al(Al(O.F2))SiO4  Orthorhombic 

Andalusite  Al(AlO)SiO4  Orthorhombic 

Sillimanite  Al(AlO)SiO4  Orthorhombic 

Datolite  Ca(B.OH)SiO4  Monoclinic 

Ca2Al2  ( Al.  O  H )  ( SiO4 )  3  Orthorhombic 

Epidote  Ca., A12(  Al.  O  H  )  ( SiO4)3  Monoclinic 

Axinite  Complex  Triclinic 

Prehnite  H2Ca2Al2(SiO4)3  Orthorhombic 

BIOTITE,  PHLOGOPITE  and  MUSCOVITE,  although  derivatives  of 
orthosilicic  acid,  are,  according  to  the  system  of  Dana,  classified 
as  hydrous  silicates,  while  the  probable  orthosilicates,  CHONDRO- 
DITE  and  STAUROLITE  are  classed  as  subsilicates. 


SILICA   AND    THE  SILICATES.  395 

NEPHELITE.— Elaeolite. 

'  COMPOSITION.— /NaAlSiO,  +  NaAl(SiO3)2.  With  partial  re- 
placement of  Na  by  K  or  Ca. 

GENERAL  DESCRIPTION. — Small,  glassy,  white  or  colorless  grains 
or  hexagonal  prisms  with  nearly  flat  ends,  in  lavas  and  eruptive 
rocks,  or  translucent  reddish-brown  or  greenish  masses  and  coarse 
crystals,  with  peculiar  greasy  lustre. 

Physical  Characters.    H.,  5.5  to  6.     Sp.  gr.,  2.55  to  2.65. 
LUSTRE,  vitreous  or  greasy.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white,  colorless,  reddish,  brownish,  greenish  or  gray. 
CLEAVAGE,  prismatic  and  basal. 

BEFORE  BLOWPIPE,  ETC. — Fuses  to  a  colorless  glass.  When 
heated  with  cobalt  solution,  becomes  blue.  Soluble  in  hydro- 
chloric acid,  with  residue  of  gelatinous  silica. 

VARIETIES. — The  usually  massive  varieties,  with  greasy  lustre, 
are  called  elseolite. 

REMARKS. — Nephelite  occurs  in  eruptive  rocks  and  lavas.  Elseolite  occurs  in 
granular,  crystalline  rocks  such  as  syenite.  Nephelite  alters  easily  and  is  the  source 
of  many  of  the  zeolites.  Austin,  Texas ;  Litchfield,  Me.,  and  the  Ozark  Mountains, 
Arkansas,  are  important  localities  of  elaeolite.  Nephelite  is  abundant  in  the  lavas  of 
Vesuvius. 

Cancrinite.  —  H6Na6Ca(Na.iCO3).2Al8(SiO4)9  is  a  yellow  to  white  (rarely  blue) 
massive  mineral  usually  associated  with  elaeolite  and  blue  sodalite.  Rarely  in  hex- 
agonal prisms.  Optically — .  It  is  found  at  Litchfield  and  Gardiner,  Me.  ;  Miask, 
Urals  ;  Brevik,  Norway  and  other  localities. 


Sodalite. — Na4(AlCl)Ala(SiO4)s  is  found  in  bright  blue  to  gray  masses  and  em- 
bedded grains.  Concentric  nodules  resembling  chalcedony  and  rarely  dodecahedral 
crystals  sometimes  of  a  pale  pink  color.  It  occurs  at  Litchfield,  Me.,  various  localities 
in  Montana,  Quebec,  and  Ontario  ;  also  in  Vesuvius  lavas,  at  Kaiserstuhl,  Baden  ;  and 
Miask,  Urals. 

Hauynite.  —  2(Na2Ca)Al!!(SiO4)r(Na.[.Ca)SO4  possibly,  but  very  complex  and 
with  varying  proportions  of  Na  and  Ca.  Occurs  as  glassy  blue  to  green  imbedded  grains, 
or  rounded  isometric  crystals  in  igneous  rock. 


Noselite.  —  Like  haiiynite  but  containing  little  or  no  lime. 


396  DESCRIPTIVE  MINERALOGY. 

LAPIS  LAZULI  or  LAZURITE.— Native  Ultramarine. 

COMPOSITION. — An  orthosilicate  of  sodium  and  aluminium,  with  a  sulphate  and 
a  polysulphide  of  sodium. 

GENERAL  DESCRIPTION. — Deep-blue  masses  intimately  mixed  with  other  minerals. 
Rarely  in  isometric  forms. 

PHYSICAL  CHARACTERS. — Translucent.  Lustre,  vitreous.  Color,  deep-blue,  violet 
and  greenish-blue.  Streak,  white.  H.,  5  to  5.5.  Sp.  gr.,  2.38  to  2.45.  Brittle. 

BEFORE  BLOWPIPE,  ETC. — Fuses  easily  to  a  white  glass,  with  intumescence.  In 
closed  tube,  glows  with  a  green  light  and  yields  water.  Soluble  in  hydrochloric  acid 
with  evolution  of  hydrogen  sulphide  and  residue  of  gelatinous  silica. 

0 

USES. — It  is  employed  in  inlaid  work,  and  before  the  invention  of  artificial  ultra- 
marine it  was  very  valuable  as  a  durable,  deep  blue,  color  for  oil  paintings. 

GARNET. 

COMPOSITION.— R"3R'"2(SiO4)3.  R"  is  Ca,  Mg,  Fe  or  Mn. 
R'"  is  Al,  Fe'"  or  Cr,  rarely  Ti. 

GENERAL  DESCRIPTION. — Imbedded  isometric  crystals,  either 
complete  or  in  druses  and  granular,  lamellar  and  compact  masses. 
Usually  of  some  brown,  red  or  black  color,  but  occurring  of  all 
colors  except  blue,  and  harder  than  quartz.  Also  found  in  alluvial 
material  as  rounded  grains. 

FIG.  533. 


Trapezohedral  Garnet,  Russell,  Mass.     N.  Y.  State  Museum. 


CRYSTALLIZATION.  —  Isometric.     Usually  a  combination  of  the 
dodecahedron  d  and  the  tetragonal  trisoctahedron,  n  =  (a  :  20, :  20) ; 


SILICA    AXD    THE   SILICATES.  397 

FIG.  534.  FIG.  535.  FIG.  536. 


[211],  Fig.  536,  or  these  as  simple  forms,  Figs.  534,  535,  or  more 
rarely  with  the  hexoctahedron,  s  =  (a  :  f#  :  30) ;  {321},  Fig.  164. 
Index  of  refraction  for  red  light  1.7645  to  1.7716. 

Physical  Characters.     H.,  6.5  to  7.5.     Sp.  gr.,*  3.15  to  4.38. 
LUSTRE,  vitreous  or  resinous.          TRANSPARENT  to  opaque. 
STREAK,  white.  TENACITY,  brittle  to  tough. 

COLOR,  brown,  black,  violet,  yellow,  red,  white,  green. 
CLEAVAGE,  dodecahedral,  imperfect. 

BEFORE  BLOWPIPE,  ETC. — Fuses  rather  easily  to  light  brown 
glass,  except  in  case  of  infusible  chromium  and  yttrium  varieties. 
Insoluble  before  fusion,  but  after  fusion  will  usually  gelatinize  with 
hydrochloric  acid.  Bead  reactions  vary  with  composition. 

VARIETIES. 

Grossularite.—  Ca3Al2(SiO4)3.  White,  pale  yellow,  pale-green, 
brown-red  rose-red. 

Pyrope. — Mg3Al2(SiO4)3  Deep-red  to  nearly  black,  often  trans- 
parent. 

Almandite, — Fe3Al2(SiO4)3.  Fine  deep-red  to  black.  Includes 
part  of  precious  and  of  common  garnet. 

Spessartite. — Mn3Al2(SiO4)3.  Brownish-red  to  purplish  hyacinth 
red. 

Andradite. — CajFe^SiOJ,.  Yellow,  green,  red,  brown,  black. 
Includes  many  of  the  common  garnets. 

Uvarovite. — Ca3Cr2(SiO4)3.     Emerald  green,  small  crystals. 

REMARKS. — Garnet  is  common  in  schists,  gneiss,  etc.,  and  also  occurs  in  granites, 
limestone,  serpentine,  and  even  in  volcanic  rocks.  By  oxidation  of  their  ferrous  iron 
and  by  the  action  of  carbonated  waters,  garnets  are  altered,  forming  calcite,  iron  ores, 
soapstone,  serpentine,  gypsum,  etc.  The  common  garnet  is  a  very  common  mineral 
in  many  localities  throughout  the  United  States.  Precious  garnets  are  found  on  the 
Navajo  Reservation,  New  Mexico ;  in  Southern  Colorado,  Arizona,  Utah,  Elliot 


DESCRIPTIVE  MINERALOGY. 


County,  Ky, ;  Amelia  County,  Va. ;  Oxford  County,  Me. ;  and  in  North  Carolina, 
Georgia,  Montana,  Idaho  and  Alaska.  In  Lewis  and  Warren  Counties,  N.  Y. ;  Raburn 
County,  Ga.,  and  Burke  County,  N.  C.,  garnets  are  so  plentiful  that  they  are  mined 
for  use  as  an  abrasive. 

USES. — Thousands  of  tons  are  used  as  an  abrasive  material  in- 
termediate in  hardness  between  quartz  and  corundum.  A  marble 
containing  large  pink  garnets  is  quarried  at  Morelos,  Mexico,  as 
an  ornamental  stone.  Transparent  red  garnets  are  sometimes 
highly  valued  as  gems,  and  the  green  variety  is  also  sometimes 
cut. 

CHRYSOLITE.— Olivine,  Peridot. 

COMPOSITION.— (Mg.Fe)2SiO4, 

GENERAL  DESCRIPTION. — Transparent  to  translucent,  yellowish- 
green  granular  masses,  or  disseminated  glassy  grains,  or  olive- 
green  sand.  When  containing  much  iron,  the  color  may  be 
reddish-brown,  or  even,  by  alteration,  opaque-brown  or  opaque- 
green.  Rarely  in  orthorhombic  crystals. 

CRYSTALLIZATION. — Orthorhombic.  Axes  a:~bic=  0.465  7 :  i  : 
0.5865.  Fig.  537  shows  the  pinacoids  a,  b  and  c,  the  unit  forms  of 
pyramid,  prism,  macro  and  brachy  dome  m,  p,  o  and  d,  the  macro 
prism  /=  (a  :  2b  :  oo  c];  {210}  and  macro  pyramid  q  =  (a  :  2~b  :  c}; 

{212}. 

FIG.  537.  FIG.  538. 


Supplement  angles  are  mm  =  49°  57'  ;  pp  =  40°  5' ;  co  =  $1° 
33';  ^=49°  33'. 

Optically  -f.  Axial  plane  c.  Acute  bisectrix  normal  to  a. 
Strong  refraction  and  double  refraction  (/?  =  1.678  and  2  V=  87° 
46',  for  yellow  light).  ^-^ 

In  thin  rock  sections,  Fig.  "§39,  the  outline,  the  distinct  cleavage 
cracks  and  the  frequent  partial  alteration  to  serpentine  assist  in  its 
recognition. 


SILICA    AND    THE  SILICATES.  399 

Physical  Characters,     H.,  6.5  to  7.     Sp.  gr.,  3.27  to  3.57. 
LUSTRE,  vitreous.  TRANSPARENT  to  translucent. 

STREAK,  white  or  yellowish.         TENACITY,  brittle. 
COLOR,  yellowish-green  to  brownish-red. 

BEFORE  BLOWPIPE,  ETC. — Loses  color,  whitens,  but  is  infusible 
unless  proportion  of  iron  is  large,  when  it  fuses  to  a  magnetic  glob- 
ule. Soluble  in  hydrochloric  acid  with  gelatinization  of  silica. 

SIMILAR  SPECIES. — Differs  by  gelatinization  from  green  granular 
pyroxene.  Is  harder  than  apatite  and  less  fusible  than  tourmaline. 

REMARKS. — Of  igneous  origin,  occurring  in  basalts,  traps  and  crystalline  schists, 
associated  with  such  minerals  as  pyroxene,  enstatite,  amphibole,  labradorite,  chromite, 
etc.  By  alteration  of  its  ferrous  iron  and  by  hydration  forms  limonite  and  serpentine, 
and  the  excess  of  magnesia  usually  forms  magnesite.  Further  change  may  alter  the 
serpentine  to  magnesite,  leaving  quartz  or  opal.  Found  at  Thetford,  Vt,  Webster, 
N.  C.,  Waterville,  N.  H.,  also  in  Virginia,  Pennsylvania,  New  Mexico,  Oregon,  etc. 
Small  gems  are  found  in  the  garnet  and  sapphire  regions  of  New  Mexico,  Arizona, 
Colorado,  and  Montana. 

USES. — Transparent  varieties  are  sometimes  cut  as  gems. 


HYALOSIDERITE.  —  A  highly  ferruginous  variety  of  chrysolite,  containing  sometimes 
as  high  as  thirty  per  cent,  of  ferrous  oxide. 


FAYALITE.  —  A  chrysolite  with  nearly  all  of  the  Mg  replaced  by  Fe  so  that  the  com- 
position is  that  of  a  simple  iron  orthosilicate.  H.,  6.5.  Sp.  gr.,  4.32.  Fuses  to  a 
magnetic  globule. 

PHENACITE. 

COMPOSITION.  —  Be2SiO4  (BeO  45.55,  SiO2  54.45  per  cent.). 

GENERAL  DESCRIPTION.  —  Colorless,  transparent,  rhombohedral  crystals,  usually 
small,  frequently  lens-shaped.  Sometimes  yellowish  and  sometimes  in  prismatic  forms. 
Harder  than  quartz. 

FIG.   539.  FIG.   540. 


Florissant,  Col. 


400 


DESCRIPTIVE  MIXER ALOG Y. 


CRYSTALLIZATION.  —  Hexagonal.  Class  of  third  order  rhombohedron,  p.  48.  Axis 
c  =  0.661.  Supplement  angles  JT.T  =  75°  57'  ;  rr  =  63°  24'.  Optically  -f  . 

PHYSICAL  CHARACTERS.  —  Transparent  to  nearly  opaque.  Lustre,  vitreous.  Color, 
colorless,  yellow,  brown.  Streak,  white.  H.  7.5  to  8.  Sp.  gr.  2.97  to  3.  Brittle. 
Cleavage,  prismatic. 

BEFORE  BLOWPIPE,  ETC.  —  Infusible  and  unaffected  by  acids.  Made  dull  blue  by 
cobalt  solution. 

REMARKS.  — Occurs  with  amazon  stone,  beryl,  quartz,  topaz,  emerald,  etc.,  and  is 
sometimes  used  as  an  imitation  gem. 


WERNERITE.— Scapolite. 

COMPOSITION.  — A  silicate  of  calcium,  .and  aluminum,  of  complex 
composition.  It  contains  also  soda  and  chlorine. 

GENERAL  DESCRIPTION.  —  Coarse,  thick,  tetragonal,  "  club- 
shaped,"  crystals,  usually  quite  large  and  dull  and  of  some  gray, 
green,  or  white  color.  Cleavage  surfaces  have  a  characteristic 
fibrous  appearance.  Also  in  columnar  and  granular  masses. 


FIG.  541. 


FIG.  542. 


.     * 


Usual  form. 


Meionite  of  Vesuvius. 


CRYSTALLIZATION.  —  Tetragonal.  Class  of  third  order  pyramid, 
p.  41.  Axis  c  =  0.438.  Usually  prisms  of  first  order  ;//,  and 
second  order  a,  and  unit  pyramid  /.  Supplement  angle  //  =  43° 
45'.  Optically  —  ,  with  weak  refraction  and  double  refraction. 

Physical  Characters.     H.,  5  to  6.     Sp.  gr.,  2.66  to  2.73. 
LUSTRE,  vitreous  to  dull.  OPAQUE  to  translucent. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  gray,  green,  white,  bluish,  reddish. 
CLEAVAGE.,  parallel  to  both  prisms. 

BEFORE  BLOWPIPE,  ETC. — Fuses  with  intumescence  to  a  white 
glass  containing  bubbles.  Imperfectly  soluble  in  hydrochloric 
acid. 


SILICA   AND    THE  SILICATES. 


401 


REMARKS. — Wernerite  has  been  formed  by  heat  at  or  near  fusion.  It  is  most  abun- 
dant in  granular  limestone  near  contact  with  granite  or  similar  rock.  It  occurs  with 
pyroxene,  apatite,  garnet,  zircon,  biotite,  etc.,  and  is  changed  to  pinite,  mica,  talc,  etc , 
by  atmospheric  influence.  Especially  abundant  at  Bolton,  Mais.  Other  localities 
common  in  New  England,  New  York,  New  Jersey  and  elsewhere. 

VESUVIANITE.— Idocrase. 

COMPOSITION.  —  Ca6  [A1(OH,  F)]  Al2(SiO4)6  with  replacement  of 
Ca  by  Mn,  and  Al  by  Fe. 

GENERAL  DESCRIPTION.  —  Brown  or  green,  square  or  octagonal 
prisms  and  less  frequently  in  pyramidal  forms.  Also  in  columnar 
masses  or  granular  or  compact. 

CRYSTALLIZATION.  —  Tetragonal.  Axis  c  =  o.  5  37.  Usually  the 
unit  prism  m  with  base  c  and  unit  pyramid  /.  Prismatic  faces 
often  vertically  striated.  Supplement  angles  //  =  50°  39'  ;  cp  = 

37°  H'. 

Optically  —  (rarely  +  )  with  rather  strong  refraction  but  weak 
double  refraction  («  =  1.7226;  f=  i-7325  for  yellow  light). 


FIG.  543. 


FIG.  544. 


FIG.  545. 


Monzoni,  Tyrol. 

Physical  Characters.     H.,  6.5.     Sp.  gr.,  3.35  to  3.45. 

LUSTRE,  vitreous  to  resinous.  TRANSLUCENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  brown  or  green,  rarely  yellow  or  blue     Dichroic. 
CLEAVAGE,  indistinct,  prismatic  and  basal. 

BEFORE  BLOWPIPE,  ETC. — Fuses  easily  with  intumescence  to  a 
green  or  brown  glass.  At  high  heat  yields  water  in  the  closed 
tube.  Very  slightly  affected  by  hydrochloric  acid,  but  after  igni- 
tion is  dissolved  leaving  a  gelatinous  residue. 

SIMILAR  SPECIES. — The  crystals  and  the  columnar  structure  dis- 
tinguish it  from  epidote,  tourmaline,  or  garnet.     The  colors  are 
not  often  like  those  of  pyroxene. 
26 


DESCRIPTIVE  MINERALOGY. 


REMARKS. — Vesuvianite  occurs  most  frequently  in  metamorphic  rocks,  granular 
limestone,  serpentine,  chlorite,  gneiss,  etc.,  with  garnet,  muscovite,  calcite,  etc.  It 
alters  to  talc,  serpentine  and  calcite.  Found  at  Parsonsfield  and  Rumford  Falls,  Me., 
Warren,  N.  H.,  Newton,  N.  J.,  Amity,  N.  Y.  Also  in  California,  Ontario  and 
Quebec. 

Melilite.  — CaiaAl4(SiO4)2  with  Na,  Mg  and  Fe  replacing  Ca  and  Al,  occurs  in  short 
prisms  and  in  tabular  orthorhombic  crystals,  especially  in  leucite  and  nephelite  rocks  and 
in  melilite  basalt. 

ZIRCON. — Hyacinth. 

COMPOSITION.  —  ZrSiO4  (ZrO  67.2,  SiO2  32.8  per  cent). 

GENERAL  DESCRIPTION.  —  Small,  sharp  cut,  square  prisms  and 
pyramids  with  adamantine  lustre  and  brown  or  grayish  color. 
Sometimes  in  large  crystals  and  in  irregular  lumps  and  grains. 

CRYSTALLIZATION. — Tetragonal.  Axis  r  =  0.640.  Common 
forms :  unit  prism  m,  unit  pyramid/,  second  order  prism  a,  and  pyra- 
mids u  =  (a:a:sc);  {331}  and  x  =  (a  \  ^a  :  3^-) ;  {311}.  Supple- 
ment angles// =56°  41';  7^=83°  9';  mu  =  20°  12';  rtur==3i°53'. 

Optically  +  with  strong  refraction  and  double  refraction  («  = 
1.9239  ;  f  =  1.9628  for  yellow  light). 


FIG.  546. 


FIG.  547. 


FIG.  548. 


FIG.  549. 


Physical  Characteis.     H.,  7.5.     Sp.  gr.,  4.68  to  4.70. 

LUSTRE,  adamantine.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  brown,  reddish,  gray,  colorless,  green,  yellow. 
CLEAVAGES,  imperfect,  parallel  to  both  pyramid  and  the  prism. 

BEFORE  BLOWPIPE,  ETC. — Infusible,  losing  color  and  sometimes 
becoming  white.  Insoluble  in  acids  or  in  soda. 

REMARKS. — Zircon  is  one  of  the  first  formed  rock  constituents,  and  is  common  as  an 
enclosure  in  the  others,  especially  the  older  eruptive  rocks,  granular  limestone,  schists, 
gneiss,  syenite,  granite,  and  iron  ore.  It  is  also  found  in  alluvial  deposits. 


SILICA   AND    THE  SILICATES. 


403 


Zircons  have  been  mined  at  Green  River,  Henderson  county,  N.  C.,  where  they  are 
especially  abundant.  Specimen  localities  are  common  throughout  the  United  States 
and  Canada. 

USES. — As  a  source  of  zirconium  oxide  used  in  one  variety  of 
incandescent  light.  Transparent,  red  and  brown  varieties  are  cut 
under  the  name  of  hyacinth.  Colorless  or  smoke  varieties  are  called 
jargon,  and  are  comparatively  worthless. 

TOPAZ. 

COMPOSITION.— Al12Si6O25Fi0  or  Al(Al(O.F2))SiO4. 

GENERAL  DESCRIPTION. — Hard,  colorless  or  yellow  transparent 
orthorhombic  crystals  with  easy  basal  cleavage.  Also  massive  in 
columnar  aggregates,  and  as  rolled  fragments  and  crystals  in  allu- 
vial deposits. 

CRYSTALLIZATION.  —  Orthorhombic.     a  :  1) :  c  =  0.529  :  i :  0.477. 

Prisms  often  vertically  striated.  Crystals  rarely  doubly  termi- 
nated. The  predominating  forms  are  the  unit  prism  ;//,  brachy 

FIG.  550.  FIG.  551.  FIG.  552. 


Omi,  Japan. 

prism  /  =  (2(1  : 1  :  oo  c) ;  { 1 20}  (with  predominance  of  /  the  section 
is  often  nearly  square);  base  c,  unit  pyramid  /  and  dome /  = 
(oo  d  :  b  :  2c) ;  {021}. 

Supplement  angles  are :  mm=  55°  43';  //=  93°  1 i' ;  //  =  38°  ; 
/-(top)  =  87°  1 8'. 

Optically  +.     Axial  plane  b.     Acute  bisectrix   normal   to  r. 
Refractive  indices  and  axial  angles  vary  considerably  for  different 
localities. 
Physical  Characters.     H.,  8.     Sp.  gr.,  3.4  to  3.65. 

LUSTRE,  vitreous.  TRANSPARENT  to  nearly  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,   colorless,   yellow,  pale-blue,  green,  white,  pink. 
CLEAVAGE,  basal  perfect. 


404 


DESCRIPTIVE  MINER ALOG  Y. 


BEFORE  BLOWPIPE,  ETC. — Infusible,  but  yellow  varieties  may 
become  pink.  With  cobalt  solution  the  powder  becomes  blue. 
Slowly  dissolved  in  borax.  If  powdered  and  heated  with  previ- 
ously fused  salt  of  phosphorus  in  open  tube  the  glass  will  be 
etched.  Insoluble  in  acids. 

REMARKS. — Probably  always  formed  under  the  influence  of  heat.  Occurs  with 
minerals  of  similar  origin  in  granite  and  gneiss,  or  less  frequently  in  cavities  in  vol- 
canic rock.  Associates  are  the  granite  minerals  and  apatite,  fluorite,  cassiterite,  beryl, 
zircon,  etc. 

Fine  crystals  of  Topaz  are  found  at  Deseret,  Utah,  at  Crystal  Park,  Cheyenne,  and 
Devil's  Head  Mountain,  Colo.,  Nathrop,  Cal.,  Stoneham,  Me.,  and  Bald  Mountain, 
N.  H.  Gems  are  also  obtained  from  Siberia,  Brazil,  Japan,  Australia,  Mexico  and 
other  countries. 

USES. — Transparent  varieties  are  cut  as  gems. 


ANDALUSITE.— Chiastolite. 

COMPOSITION.— Al(AlO)SiO4,  (A12O3  63.2,  SiO2  36.8  per  cent.) 
GENERAL  DESCRIPTION. — Coarse,  nearly  square  prisms  of  pearl 
gray  or  pale  red  color,  or  in  very  tough,  columnar  or  granular 
masses.  An  impure  soft  variety  (chiastolite)  occurs  in  rounded 
prisms,  any  cross  section  of  which  shows  a  cross  or  checkered 
figure,  due  to  the  symmetrical  deposition  of  the  impurities,  p.  133. 


FIG.  553. 


FIG.  554. 


CRYSTALLIZATION.  —  Orthorhombic.  Axes  a  \]b  :  c  =  0.986  :  i  : 
0.702.  Usually  either  the  unit  prism  ;;/,  and  base  c,  or  these  with 
the  unit  brachy  dome  d.  Supplement  angles  are  mm  =  89°  12'  ; 
dd=  70°  10'. 

Optically  — .  Axial  plane  the  brachy-pinacoid.  Acute  bisec- 
trix normal  to  c.  Colored  varieties  strongly  pleochroic. 


SILICA   AND    THE  SILICATES. 


405 


Physical  Characters.     H.,  7  to  7.5.     Sp.  gr.,  3.16  to  3.20. 
LUSTRE,  vitreous.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle  to  tough. 

COLOR,  rose-red,  flesh-red,  violet,  pale  green,  white,  pearl-gray. 
CLEAVAGE,  prismatic,  imperfect  at  angle  of  90°  48'. 

BEFORE  BLOWPIPE,  ETC. — Infusible.  In  powder  becomes  blue 
with  cobalt  solution.  Insoluble  in  acids. 

REMARKS. — It  occurs  in  clay  slates  and  in  gneiss  and  schists  with  cyanite,  fibro- 
lite,  quartz,  etc.  It  alters  rather  readily  to  cyanite  or  kaolin.  Found  in  many 
localities  in  the  New  England  States,  also  in  Pennsylvania  and  California.  Foreign 
localities  are  numerous.  Transparent  crystals  are  found  in  Minas  Geraes,  Brazil. 


SILLIMANITE  or  FIBROLITE. 

COMPOSITION— Al(AlO)SiO4.  /4  £  •> •  "*• 

GENERAL  DESCRIPTION. — Long,  almost  fibrous  orthorhombic  crystals,  and  fibrous 
or  columnar  masses  of  brown  or  gray  color. 

PHYSICAL  CHARACTERS.— Transparent  to  translucent.  Lustre,  vitreous.  Color, 
brown,  gray,  greenish.  Streak,  white.  H.,  6  to  7.  Sp.  gr.,  3.23  to  3.24.  Tough. 
Cleavage,  parallel  to  brachy  pinacoid. 

BEFORE  BLOWPIPE,  ETC. — Infusible,  becomes  dark  blue  with  cobalt  solution.  In- 
soluble in  acids. 

REMARKS. — Chiefly  found  in  mica  schist,  gneiss,  etc.     Sometimes  with  andalusite. 

USES. — In  the  stone  age  it  was  used  for  tools,  weapons,  etc.,  being  second  only  to 
jade  in  toughness. 

DATOLITE. 

COMPOSITION.— Ca(B.OH)SiO4. 

GENERAL  DESCRIPTION. — Highly  modified,  glassy,  monoclinic 
crystals  often  lining  a  cavity  in  a  basic  rock.  Usually  colorless, 
but  also  white  or  greenish.  Also  in  compact,  dull,  white  or  pink 
masses,  resembling  unglazed  porcelain. 


FIG.  555. 


FIG.  556. 


FIG.  557. 


Bergen  Hill,  N.  J. 


Lake  Superior. 


406  DESCRIPTIVE  MINERALOGY. 

CRYSTALLIZATION.  —  Monoclinic.  ,3  =  89°  51'.  Axes  a  :  1 : 
c  =.  0.634  :  I  :  1.266.  Prominent  forms  are  the  pinacoids  a  and 

c,  the  unit  prism  m,  negative  unit  pyramid  J5,   unit  clino-dome 

d,  clino-prism  /=  (2a  :  b  :  ooc),  { 120}  ;  and  positive  hemi-pyramid 
r—  (a  :  ~b  :  %c),   {112}.      Supplement  angles  are  mm  =  64°  47'  ; 
//=  76°  29'  ;  Jp=  59°  5'  ;  dd=  103°  23'. 

Physical  Characters.     H.,  5  to  5.5.     Sp.  gr.,  2.9  to  3. 

LUSTRE,  vitreous.  TRANSLUCENT  to  nearly  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  colorless,  white,  greenish. 

BEFORE  BLOWPIPE,  ETC. — In  forceps  or  on  charcoal  fuses  easily 
to  a  colorless  glass,  and  if  mixed  with  a  flux  of  acid  potassium 
sulphate  and  calcium  fluoride  and  a  little  water  it  will  color  flame 
green.  In  closed  tube  yields  water  at  a  high  heat.  Soluble  in 
hydrochloric  acid,  with  gelatinization. 

SIMILAR  SPECIES.  —  Differs  from  the  zeolites  in  crystalline  form 
and  flame  and  from  colemanite  by  gelatinization. 

REMARKS.  —  It  is  a  secondary  mineral  found  in  basic  eruptive  rocks  and  sometimes 
in  metallic  veins.  Often  occurs  with  the  zeolites,  prehnite,  calcite,  etc.  Found  at 
Bergen  Hill  and  Paterson,  N.  ].  ;  at  Hartford,  Tariffville  and  Roaring  Brook,  Conn. 
Also  in  New  York,  Michigan,  Massachusetts,  California,  etc. 

ZOISITE.— Thulite. 

COMPOSITION.  —  Ca2Al2(Al.OH)  (SiO4)3. 

GENERAL  DESCRIPTION. — Gray  or  green  and  rose  red  (thulite)  columnar  and 
fibrous  aggregates.  More  rarely,  deeply  striated  orthorhombic  prisms  with  indistinct 
terminations  and  perfect  cleavage  parallel  to  the  brachy-pinacoid. 

PHYSICAL  CHARACTERS.  —  Transparent  to  opaque.  Lustre,  vitreous  to  pearly. 
Color,  white,  gray,  brown,  green,  pink  and  red.  Streak,  white.  H.,  6-6.5.  Sp.  gr., 
3.25-3.35.  Optically  4-. 

BEFORE  BLOWPIPE,  ETC.  —  Swells  up  and  fuses  easily  to  a  glassy  mass  which  does 
not  readily  assume  globular  form.  Not  affected  by  HC1  before  ignition,  but  after  igni- 
tion it  is  decomposed  with  formation  of  jelly. 

REMARKS. — Found  at  Ducktown,  Tenn.,  Chesterfield,  Mass.,  Uniontown,  Pa.,  and 
many  other  localities. 

EPIDOTE. 

COMPOSITION.  —  Ca.,Al2(AlOH)(SiO4)3  with  some  iron  replacing 
aluminum. 

GENERAL  DESCRIPTION.  —  Coarse  or  fine  granular  masses  of 
peculiar  yellowish-green  (pistache  green)  color,  sometimes  fibrous- 


SILICA   AND    THE  SILICATES. 


407 


Also  in  monoclinic  crystals  and  columnar  groups,  from  yellow- 
green  to  blackish-green  in  color. 

FIG.  558. 


Epidote,  Sulzbach,  Tyrol.     N.  Y.  State  Museum. 


37''     Axes  a  :  ~b  : 
unit  prism,  a  and  c 

FIG.  559. 


CRYSTALLIZATION.  —  Monoclinic.     ,2  =  64 
c  =  1.579  :  l  '•  1-804.     Common  forms  :  ;//  = 
pinacoids,  /  unit  pyramid  and  o  unit  dome. 
Supplement  angles   are    mm=  109°  56'  ; 
ca  =  64°  37'  ;   co  =  63°  42'.    Crystals  ex- 
tended in  the  direction  of  the  ortho-axis. 

Optically    — .     Axial    plane  the  clino- 
pinacoid.      Acute  bisectrix  nearly  vertical. 

Refraction  and  double  refraction  both  strong.  Pleochroism  strong. 
Sometimes  shows  colored  absorption  figure  when  held  close  to 
the  eye. 

Physical  Characters.     H.,  6  to  7.     Sp.  gr.,  3.25  to  3.5. 

LUSTRE,  vitreous.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  yellowish-green  to  nearly  black  and  nearly  white,  also 
red  and  gray.  CLEAVAGE,  basal,  easy. 

BEFORE  BLOWPIPE,  ETC. — Fuses  easily  with  intumescence  to  a 
dark,  usually  slightly  magnetic,  globule.  At  high  heat  yields 
water.  Slightly  soluble  in  hydrochloric  acid,  but  if  previously 
ignited,  it  dissolves,  leaving  gelatinous  silica. 


408  DESCRIPTIVE  MINERALOGY. 

REMARKS. — Formed  chiefly  by  alteration  of  the  feldspars,  hornblende  or  biotite, 
etc.,  and  is  common  in  many  crystalline  rocks,  often  accompanying  beds  of  iron  in  these 
rocks.  It  is  not  readily  altered.  Common  throughout  New  England  and  many  of  the 
western  States. 

Piedmontite.  —  A  red  manganiferous  epidote.  Crystals  show  different  colors  by 
transmitted  light  when  viewed  through  different  planes. 


Allanite.  —  A  silicate  of  the  cerium  and  yttrium  groups  with  lime  and  iron.  Occurs 
in  pitch  black  or  brownish  embedded  veins  and  masses  and  flat  tabular  or  prismatic 
monoclinic  crystals. 

AXINITE.  FIG.   560. 

COMPOSITION.  —  An  orthosilicate  containing,  especially, 
boron,  aluminium,  and  calcium  with  some  iron  and  man- 
ganese. 

GENERAL  DESCRIPTION.  —  Occurs  in  acute-edged  tri- 
clinic  crystals,  see  Fig.  $60,  usually  of  clove  brown,  bluish 
or  yellow  color.  Also  occurs  lamellar  or  massive  with 
bright  glassy  lustre. 

PHYSICAL  CHARACTERS.  —  Translucent  to  transparent. 
Lustre,  highly  vitreous.  Color  brown,  bluish,  yellow, 
gray  and  greenish.  Streak,  white.  H.,  6.5-7.  Sp.  gr., 
3.25-3.27.  Optically—. 

BEFORE  BLOWPIPE,  ETC.  —  Fuses  easily  with  bubbling  to  a  dark  greenish  or  black 
glassy  globule.  Reacts  for  boron.  Gelatinizes  with  HC1  after  ignition. 

REMARKS. — Fine  crystals  are  obtained  in  Bourg  d'Oisans,  Dauphine  ;  and  Mt. 
Skopi,  Switzerland. 

PREHNITE. 

COMPOSITION.  —  H2Ca2Al2(SiO4)3. 

GENERAL  DESCRIPTION. — A  green  to  grayish-white  vitreous 
mineral.  Sheaf-like  groups  of  tabular  crystals,  united  by  the  basal 
planes.  Sometimes  barrel-shaped  crystals  and  frequently  reniform 
or  botryoidal  crusts,  Fig.  270,  with  crystalline  surface. 

Physical  Characters.     H.,  6  to  6.5.     Sp.  gr.,  2.8  to  2.95. 
LUSTRE,  vitreous.  TRANSLUCENT. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  light  to  dark  green  or  grayish-white.   CLEAVAGE,  basal. 

BEFORE  BLOWPIPE,  ETC. — Easily  fusible  to  a  whitish  glass  con- 
taining bubbles.  In  closed  tube  yields  a  little  water.  Soluble  in 
hydrochloric  acid,  and  after  fusion  is  soluble  with  a  gelatinous 
residue. 

SIMILAR  SPECIES. — Resembles  calamine  or  green  smithsonite 
somewhat,  but  is  more  easily  fused,  and  does  not  gelatinize  unless 
previously  ignited. 


SILICA   AND    THE  SILICATES.  409 

REMARKS. — Occurs  in  granite  gneiss,  trap,  syenite,  etc.,  as  a  secondary  mineral 
derived  from  their  alteration,  and  associated  with  other  secondary  minerals  as  datolite 
or  the  zeolites.  Bergen  Hill  and  Paterson,  N.  J.,  have  furnished  a  few  gem  stones. 
Other  localities  are  Farmington,  Conn.,  the  Tamarack  and  Quincy  copper  mines,  Mich., 
Perry,  Me.,  and  Westport,  N.  Y. 

USES. — To  a  limited  extent  has  been  cut  as  a  gem. 

BASIC  OR  SUBSILICATES. 

Made  a  division  by  Dana  because  their  constitution  is  not  defi- 
nitely settled,  though  probably  each  belongs  to  one  of  the  preced- 
ing groups. 

Here  are  described  : 

Chondrodite  H2Mg19Si8OS4F4  Monoclinic 

Tourmaline  R18B2(SiO5)4  Hexagonal 

Staurolite  Fe(AlO)4(Al.OH)(SiO)4  Orthorhombic 

CHONDRODITE. 

COMPOSITION.— HjMg^SigO^F^  or  (Mg.Fe)ls(Mg.Fj4(MgOH)!1(SiO4)8,  with  some 
iron  replacing  magnesium. 

GENERAL  DESCRIPTION. — The  chemical  compound  occurs  as  three  crystal lograph- 
ically  distinct  species,  chondrodite,  humite,  clinohumite.  Chondrodite  proper  consists 
of  compact  brown  masses  or  disseminated  grains  and  yellowish-brown  to  red,  mono- 
clinic,  pseudo  orthorhombic,  crystals  of  great  complexity. 

PHYSICAL  CHARACTERS. — Translucent.  Lustre,  vitreous.  Color,  brown,  garnet- 
red,  light  to  dark  yellow.  Streak,  white.  H.,  6  to  6.5.  Sp.  gr.,  3.1  to  3.2.  Brittle. 

BEFORE  BLOWPIPE,  ETC  — Infusible,  sometimes  blackens  and  then  turfts  white. 
Fused  with  powdered  salt  of  phosphorus  glass  will  yield  fluorine.  Soluble  in  hydro- 
chloric acid  with  gelatinization. 

REMARKS. — Chiefly  found  in  crystalline  limestone  or  with  other  magnesium  minerals. 
Alters  to  serpentine. 

TOURMALINE.— Schorl. 

COMPOSITION.— R18B2(SiO6)4.     R  chiefly  Al,  K,  Mn,  Ca,  Mg,  Li. 

GENERAL  DESCRIPTION. — Prismatic  crystals,  the  cross  sections 
of  which  frequently  show  very  prominently  a  triangular  prism. 
Color,  usually  some  dark  smoky  or  muddy  tint  of  black,  brown  or 
blue,  also  bright  green,  red,  and  blue,  or  rarely  colorless.  Some- 
times the  centre  and  outer  shell  are  different  colors,  as  red  and 
green.  Sometimes  the  color  is  different  at  two  opposite  ends. 
Occurs  also  columnar  in  bunches  or  radiating  aggregates  and  in 
compact  masses. 

CRYSTALLIZATION.  —  Hexagonal.  Hemimorphic  class,  p.  46. 
Axis  c  =  0.448. 


4io 


DESCRIPTIVE  MINERALOGY. 


Prevailing  forms  :  trigonal  prism  m,  second  order  prism  a,  unit 
rhombohedron  /,  negative  rhombohedron  f=(a:  co  a  :  a  :  2e), 
{ 202 1 } .  Supplement  angles  are  :  //  =  46°  5 2'  ;  /"=  77°  ;  mp  = 
62°  40'. 

Optically  — .  Strongly  dichroic,  absorption  very  marked  for  rays 
vibrating  parallel  to  the  vertical  axis.  Double  refraction  rather 
strong. 

FIG.  561.  FIG.  562.  FIG.  563. 


Physical  Characters.     H.,  7  to  7.5.     Sp.  gr.,  2.98  to  3.20. 
LUSTRE,  vitreous  or  resinous.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  black,  brown,  green,  blue,  red,  colorless. 
CLEAVAGE,  difficult,  parallel  to  R  and  i-  2. 

BEFORE  BLOWPIPE,  ETC. — Usually  fuses,  sometimes  very  easily. 
With  a  paste  of  KHSO4)CaF2  and  water  it  yields  a  green  flame. 
Insoluble  in  acids,  but  after  strong  ignition  gelatinizes. 

SIMILAR  SPECIES. — Differs  from  hornblende  in  hardness,  crystal- 
line form  and  absence  of  prismatic  cleavage.  Differs  from  garnet 
or  vesuvianite  in  form,  difficult  fusion,  and  green  flame. 

REMARKS. — Occurs  in  crystalline  rocks:  granite,  gneiss,  mica-schists,  crystalline 
limestone,  etc.,  with  many  associates.  By  alteration  it  forms  cookeite,  lepidolite,  talc, 
and  chlorite.  Tourmalines  of  gem  value  have  been  obtained  in  some  quantity  from 
Paris,  Auburn,  and  Hebron,  Me.,  and  from  Riverside  county,  California. 

USES. — Transparent,  red,  yellow,  and  green  varieties  are  cut  as 
gems.  Thin  plates  are  used  to  polarize  light. 

STAUROLITE. 

COMPOSITION.— Fe(AlO)4(AlOH)(SiO4)2,  but  varying.  May  con- 
tain Mg  or  Mn. 

GENERAL  DESCRIPTION. — Dark  brown  to  nearly  black  ortho- 
rhombic  prisms  often  twinned,  or  in  threes,  crossing  at  90°  and 
120°.  Surfaces  bright  if  unaltered.  Very  hard. 


SILICA   AND    THE  SILICATES. 
FIG.  564. 


411 


Tourmaline  in  Lepidolite,  San  Diego  Co.,  Cal.     N.  Y.  State  Museum. 

CRYSTALLIZATION.  —  Othorhombic.  Axes  d  :  ~b  :  c  =  0.473  :  l  '• 
0.683.  Usual  forms :  unit  prism  m,  unit  dome  o  and  pinacoids  b 
and  c.  Frequently  in  twins  crossed  nearly  at  right  angles,  Fig. 
566,  or  nearly  at  60°,  Fig.  567. 

Supplement  angles  are  :  mm  =  50°  40' ;  ^=55°  14'.  Opti- 
cally -f.  Axial  plane  the  macro-pinacoid.  Acute  bisectrix, 
normal  to  c. 

FIG.  565  FIG.  566.  FIG.  567. 


Physical  Characters.     H.,  7  to  7.5.     Sp.  gr.,  3.65  to  3.75. 
LUSTRE,  resinous  or  vitreous.  TRANSLUCENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  dark  brown,  blackish-brown,  gray  when  weathered. 
CLEAVAGE,  parallel  to  brachy  pinacoid. 


412  DESCRIPTIVE  MINERALOGY. 

BEFORE  BLOWPIPE,  ETC. — Infusible,  except  when  manganiferous. 
Partially  soluble  in  sulphuric  acid. 

REMARKS. — Occurs  chiefly  in  schistose  rock  with  andalusite,  garnet,  tourmaline, 
cyanite,  etc.,  but  is  not  found  in  schists  rich  in  amphibole.  Abundant  at  Claremont, 
Grantham,  and  Lisbon,  N.  H.,  at  Windham,  Me.,  Chesterfield,  Mass.,  Litchfield, 
Conn.,  and  several  other  localities  in  New  England.  Also  in  New  York,  North 
Carolina,  Georgia,  and  Pennsylvania. 

HYDROUS  SILICATES. 

Compounds  containing  water  of  crystallization  with  certain 
closely  related  species  in  which  the  water  plays  the  part  of  a  base 
or  is  in  doubt. 

The  minerals  described  here  are : 

ZEOLITE   DIVISION. 


Apophyllite  H14K2Cag(SiO3)16  +  gU3O  Tetragonal 

Heulandite  H4CaAl2(SiOs)6-f  3H2O  Monoclinic 

Stilbite  H4(Na.,Ca)Al2(SiO3)6+4H2O  Monoclinic 

Chabazite  (Ca.Na2)Al.i(SiOs)4  +  6H2O  Hexagonal 

Analcite  NaAl(SiO3)2+ H2O  Tetragonal 

Natrolite  Na2Al  ( A1O )  ( SiO3)3  -f  2H,O  Orthorhombic 

MICA   DIVISION. 

Muscovite  H2(K.Na)Al3(SiO4)3  Monoclinic 

Biotite  (H.K),(Mg.Fe),Alf(SiO4)a  Monoclinic 

Phlogopite  RsMg,Al(Si04),  Monoclinic 


Chlorite  Silicate  of  H,  Mg,  Fe,  Al  Monoclinic 

SERPENTINE   AND   TALC   DIVISION. 

Serpentine  H4Mg3Si2O9 

Talc  H.,Mg.j(SiO3)4  Monoclinic 

Sepiolitc  H4Mg2Si3010 

KAOLIN  DIVISION. 

Kaolinite  H4Al2SliO,  Monoclinic 

Pyrophyllite  HAl(SiO3),  Monoclinic 

ZEOLITES. 

The  zeolites  are  a  group  of  silicates,  all  of  which  are  of  a  sec- 
ondary origin  and  are  usually  found  in  the  seams  or  cavities  of 
basic  igneous  rocks,  such  as  basalt  or  diabase,  and  less  frequently 
in  granite  or  gneiss. 


SILICA   AND    THE  SILICATES. 


413 


They  are  similar  to  the  feldspars  in  constituents  and  combining 
ratios,  and  are  chiefly  formed  from  the  feldspars  and  from  nephe- 
lite,  leucite,  etc.  Most  of  them  fuse  easily,  with  appearance  of 
boiling,  and  all  contain  water  of  crystallization.  The  hardness 
varies  from  3.5  to  5.5,  and  the  specific  gravity  from  2.0  to  2.4. 

APOPHYLLITE. 

COMPOSITION. — HuK2Ca8(SiO3)16  +  9H2O,  with  replacement  by 
fluorine. 

GENERAL  DESCRIPTION. — Colorless  and  white  or  pink,  square 
crystals.  Sometimes  flat,  square  plates  or  approximate  cubes ;  at 
other  times  pointed  and  square  to  nearly  cylindrical  in  section. 
Notably  pearly  on  base  or  may  show  in  vertical  direction  a  peculiar 
— fish  eye — internal  opalescence.  Found  occasionally  in  lamellar 
masses. 

CRYSTALLIZATION. — Tetragonal.  Axis  c=  i . 2 5  2.  Usually  com- 
binations of  unit  pyramid  /,  base  c,  and  second  order  prism  a. 
Supplement  angle  pp  =  76°  ;  cp  =  60°  32'.  Prism  faces  vertically 
striated. 


FIG.  568. 


FIG.  569. 


FIG.  570. 


FIG.  571. 

Physical  Characters.     H.,  4.5  to  5.     Sp.  gr.,  2.3  to  2.4. 
LUSTRE,  vitreous  or  pearly.     TRANSPARENT  to  nearly  opaque. 
STREAK,  white.  TENACITY,  brittle. 

COLOR,  colorless,  white,  pink  or  greenish.      CLEAVAGE,  basal. 

BEFORE  BLOWPIPE,  ETC.  —  Exfoliates  and  fuses  to  a  white  enamel. 
In  closed  tube  yields  water.  In  hydrochloric  acid  forms  flakes 
and  lumps  of  jelly. 


DESCRIPTIVE   MINERALOGY. 


REMARKS.— Occurs  in  volcanic  rocks  and  mineral  veins  with  zeolites,  datolite,  pec- 
tolite,  etc.  It  is  a  secondary  mineral. 

HEULANDITE. 

COMPOSITION.  —  H4CaAl2(SiO3)6  -t-  3H2O. 

GENERAL  DESCRIPTION. — Monoclinic  crystals,  with  very  bright,  pearly,  cleavage 
surfaces.  The  face  parallel  to  the  cleavage  is  also  bright  pearly,  and  is  less  symmetri- 
cal than  the  corresponding  face  of  stilbite. 

PHYSICAL  CHARACTERS.  —  Transparent  to  translucent.  Lustre,  pearly  and  vitreous. 
Color,  white,  red,  brown.  H.,  3.5-4.  Sp.  gr.  2.18-2.22.  Brittle.  Cleaves  parallel 
to  a  pearly  face. 

BEFORE  BLOWPIPE,  ETC.  —  Exfoliates  and  fuses  easily  to  a  white  enamel.  In  the 
closed  tube  yields  water.  Soluble  in  hydrochloric  acid,  with  a  residue  of  fine  powder. 

STILBITE.  —  Desmine. 

COMPOSITION.  —  H4(Na2.Ca)  Al2(SiO3)6  +  4H2O. 

GENERAL  DESCRIPTION. — Tab- 
ular crystals,  of  white,  brown  or 
red  color,  pearly  in  lustre  on 
broad  faces  and  frequently  united 
by  these  faces  in  sheaf- like 
groups.  Sometimes  globular  or 
radiated.  Crystals  are  ortho- 
rhombic  in  appearance,  but  really 
complex  monoclinic  twins. 


FIG.  572. 


Physical  Characters.     H.,  3.5  to  4. 
LUSTRE,  vitreous  or  pearly. 
STREAK,  white. 

COLOR,  yellow,  brown,  white,  red. 
CLEAVAGE,  parallel  to  pearly  face. 


Cape  Blomidon,  N.  S. 

Sp.  gr.,  2.09  to  2.2. 
TRANSLUCENT. 
TENACITY,  brittle. 


BEFORE  BLOWPIPE,  ETC. — Swells  and  exfoliates  in  fan  shapes, 
and  fuses  easily  to  a  white,  opaque  glass.  Yields  water  in  closed 
tube.  Soluble  in  hydrochloric  acid,  with  a  pulverulent  residue. 

REMARKS. — Occurs  with  other  zeolites. 

CHABAZITE. 

COMPOSITION.  —  (Ca,  Na2)Al2(SiO3)4  +  6H2O. 

GENERAL  DESCRIPTION. — Simple  rhombohedral  crystals,  almost 
cubic,  also  in  modified  forms  and  twins.  Faces  striated  parallel 
to  edges.  Color,  white,  pale-red  and  yellow. 


SILICA   AND    THE  SILICATES. 


415 


Physical  Characters.     H.,  4  to  5.     Sp.  gr.,  2.08  to  2.16. 
LUSTRE,  vitreous.  TRANSLUCENT,  transparent. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white,  red,  yellow.  CLEAVAGE,  parallel  to  the  unit 

rhombohedron. 

CRYSTALLIZATION.  —  Hexagonal.  Scalenohedral  class,  p.  42. 
Axis  c=  i. 086.  Unit  rhombohedron  p  and  negative  rhombo- 
hedra  e  =  (a  :  oo  a  :  a  :  j^c);  {1012},  and  /=  (a:  oo  a  :  a  :  2c)  ; 
{2021}  are  most  common.  Supplement  angles  //=85C  14'; 
^=  54°  47'. 

Optically  —  usually,  sometimes  +  ;  interference  figure  confused. 

FIG.  573. 


FIG.  574. 


FIG.  575. 


BEFORE  BLOWPIPE,  ETC.  —  Intumesces  and  fuses  to  a  nearly 
white  glass  containing  bubbles.  Yields  water  in  closed  tube. 
Soluble  in  hydrochloric  acid,  leaving  flakes  and  lumps  of  jelly. 

REMARKS. — Occurs  generally  in  basaltic  rocks.  Found  in  several  localities  in 
Nova  Scotia.  Also  at  Baltimore,  Md.  ;  Aussig,  Bohemia ;  Faroer,  Greenland  ;  Rich- 
mond, Victoria. 

ANALCITE. 

COMPOSITION.  —  NaAl(SiO3)2  +  H2O. 

GENERAL  DESCRIPTION.  —  Small  white  or  colorless  trapezohe- 

FIG.  576.  FIG.  577.  FIG.  578. 


Island  of  Cyclops. 

drons,  Figs.  576,  577,  or  modified  cubes,  Fig.  578;  rarely  granular 
or  compact  with  concentric  structure. 

CRYSTALLIZATION.  —  Isometric.     The  trapezohedron  n  =  (a  :  2a 


416  DESCRIPTIVE  MINERALOGY. 

:  20)  ;    {  2 1 1 } ,  is  most  frequent  sometimes  modified  by  the  cube  a 
or  dodecahedron  d,  and  in  some  crystals  the  cube  predominates. 

Physical  Characters.— H.,  5  to  5.5.    Sp.  gr.,  2.2  to  2.29. 
LUSTRE,  vitreous.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white,  colorless,  greenish,  red. 

BEFORE  BLOWPIPE,  ETC. — Fuses  easily  and  quietly  to  a  clear, 
colorless  glass.  Yields  water  in  closed  tube.  Gelatinizes  with 
hydrochloric  acid. 

REMARKS. — A  secondary  mineral,  usually  with  other  zeolites. 

NATROLITE.  —  Needle  Zeolite. 

COMPOSITION.  —  Na2Al(AlO)  (SiO3)3  +  2H,O. 

GENERAL  DESCRIPTION.  —  Colorless  to  white,  slender,  nearly 
square  prisms,  with  very  flat  pyramids.  Usually  in  radiating  and 
interlacing  clusters  and  bunches.  Also  fibrous  granular  and 
compact. 

CRYSTALLIZATION.  —  Orthorhombic.  Axes  ft  :  b  :  c  =  0.979  : 
i  :  0.354.  Angle  of  prism  =88°  46'. 

Physical  Characters.     H.,  5  to  5.5.     Sp.  gr.,  2.2  to  2.25. 

LUSTRE,  vitreous.  TRANSPARENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  colorless,  white,  yellow,  red.  CLEAVAGE,  prismatic. 

BEFORE  BLOWPIPE,  ETC. — Fuses  very  easily  to  a  colorless  glass. 
In  closed  tube,  yields  water.  Soluble  in  hydrochloric  acid,  with 
gelatinization. 

SIMILAR  SPECIES. — Differs  from  pectolite  in  square  cross-sec- 
tion and  fusion  to  a  clear,  colorless  glass. 

REMARKS. — Occurs  with  other  zeolites  and  with  prehnite,  calcite  and  datolite. 


Thomsonite.  —  (Ca.Na,),Al4(SiO4)4  -f  5H2O.  Usually  in  radiating  fibers  or  slender 
prismatic  crystals  or  amygdaloidal  with  fibrous  structure  radiating  from  several  centers 
and  of  different  colors. 

THE  MICA  DIVISION. 

The  micas  are  common  constituents  of  granites,  gneisses  and 
schists,  and  are  characterized  principally  by  the  very  perfect  basal 
cleavage  into  elastic  flakes.  They  occur  as  monoclinic  crystals 
with  prism  angles  of  closely  120°,  which  usually  appear  either 


SILICA   AXD    THE  SILICATES.  417 

hexagonal  or  orthorhombic.  Cleavages  show  the  interference 
figure  because  the  acute  bisectrix  is  nearly  normal  to  the  base. 
In  all  the  species  a  blow  from  a  conical  point  upon  a  cleavage 
surface  develops  a  so-called  percussion  figure,  consisting  of  three 
cracks,  one  parallel  to  the  plane  of  symmetry,  the  others  at 
definite  angles  to  this. 

The  angle  between  the  optic  axes  and  the  relative  position  of 
the  axial  plane  and  the  principal  line  of  the  percussion  figure  give 
convenient  distinctions. 


MUSCOVITE.  —  Potash  Mica,  White  Mica,  Isinglass. 

COMPOSITION.  —  H2(K.Na)Al3(SiO4)3,  with  some  replacement  by 
Mg  or  Fe. 

GENERAL  DESCRIPTION.  —  Disseminated  six-sided  scales  and 
rough  crystals,  which  cleave  with  great  ease  into  thin,  elastic, 
transparent  leaves.  Also  in  masses  of  coarse  or  fine  scales  some- 
times grouped  in  globular  and  plumose  forms,  Fig.  272.  Usually 
transparent  and  pale  gray  in  color,  and  with  pearly  lustre  on  the 
cleavage  surfaces. 

CRYSTALLIZATION.  —  Monoclinic.  /3  =  89°  54'.  Prism  angle 
=  59°  48'.  Crystals  usually  rhombic  or  hexagonal  in  section, 
with  rough  faces,  and  usually  tapering.  Sometimes  very  large, 
several  feet  across.  Cleavage  is  approximately  at  right  angles  to 
the  prism. 

Optically—.  Axial  plane  at  90°  to  b  and  near  90°  to  c ;  that 
is,  at  90°  to  the  principal  line  of  the  percussion  figure.  Axial 
angle  variable  but  large,  2E  50°  to  70°.  Pleochroism  feeble. 
Absorption  in  sections  cut  at  90°  to  the  cleavage  very  strong. 

Physical  Characters.     H.,  2  to  2.5.     Sp.  gr.,  2.76  to  3. 

LUSTRE,  vitreous,  pearly  on  cleavage.     TRANSPARENT  in  laminae. 
STREAK,  white.  TENACITY,  elastic. 

COLOR,  gray,  brown,  green,  yellow,  violet,  red,  black. 
CLEAVAGE,  basal,  eminent. 

BEFORE  BLOWPIPE,  ETC. — Fuses  only  on  thin  edges  to  a  yellow- 
ish glass.  Insoluble  in  acids. 

SIMILAR  SPECIES.— Differs  from  talc  or  gypsum  in  being  elastic. 
Is  usually  lighter  colored  than  biotite. 

27 


418  DESCRIPTIVE  MINERALOGY. 

REMARKS. — Muscovite  is  of  both  igneous  and  secondary  origin.  It  occurs  with 
quartz  and  feldspars,  in  granite,  gneiss  and  mica  schist  and  related  rocks  and  more  or 
less  disseminated  in  other  rocks,  and  it  also  is  found  formed  from  cyanite,  topaz,  feld- 
spars, corundum,  etc.  The  most  productive  mica  mines  of  the  United  States  are  in 
Mitchell,  Yancey,  Jackson  and  Macon  Counties,  S.  C.,  and  Groton,  N.  H.  Other 
large  deposits  exist  at  Grafton,  N.  H. ;  Las  Vegas  and  Cribbensville,  N.  M.,  and 
Deadwood  and  the  Black  Hills,  S.  D.,  many  of  which  are  intermittently  mined.  Also 
in  Nevada,  California,  Colorado  and  Pennsylvania  in  quantity  and  quality  fit  for  use. 
Large  quantities  of  mica  are  annually  imported  from  India. 

USES.  —  In  sheets  as  transparent  material  in  doors  of  furnaces, 
stoves,  etc.  As  insulating  material  in  electrical  apparatus,  espec- 
ially on  the  armatures  of  dynamos.  Ground  as  a  coating  for  spang- 
ling wall  papers  and  such  fabrics  as  brocade  ;  producing  the  frosted 
appearance  of  Christmas  cards  ;  as  an  absorbent  of  nitro-glycerine ; 
as  a  non-conducting  material  for  heat  and  electricity  ;  for  a  lubricant 
and  for  a  mica  paint  giving  a  spangled  appearance  to  the  coated 
object. 

DAMOURITE.  —  An  altered  hydrous  potassium  mica  in  small  scales  or  fibrous. 
Cleavage  plates  less  elastic  and  of  silky  luster. 


BIOTITE. — Black  Mica,  Magnesium  Mica. 

COMPOSITION.  — An  orthosilicate  approximating  (H.K)2(Mg.Fe)2- 
Al2(Si04)3. 

GENERAL  DESCRIPTION.  —  The  most  common  of  the  micas. 
Accompanies  muscovite  in  granitic  rocks  and  schists,  but  is  usually 
dark  green  to  black  in  color  and  in  comparatively  small  scales. 
Also  as  black,  green  and  red  crystals  at  Vesuvius.  It  cleaves  into 
thin,  elastic  leaves. 

Optically  — .  Axial  plane  usually  parallel  to  b  ;  that  is  parallel 
to  the  principal  line  of  the  percussion  figure.  Axial  angle  usually 
small,  2E  varying  o  to  12°,  rarely  50°.  Pleochroism  strong. 

Physical  Characters.     H.,  2.5  to  3.     Sp.  gr.,  2.7  to  3.1. 

LUSTRE,  pearly,  vitreous,  submetallic.    TRANSPARENT  to  opaque. 
STREAK,  white.  TENACITY,  tough  and  elastic. 

COLOR,  commonly  black  to  green.   CLEAVAGE,  basal,  eminent. 

BEFORE  BLOWPIPE,  ETC. — Whitens  and  fuses  on  thin  edges. 
Decomposed  by  boiling  sulphuric  acid,  with  separation  of  scales 
of  silica. 


SILICA   AND    THE  SILICATES.  419 

REMARKS. — Occurrence  and  associates  like  muscovite,  but  is  more  common  than 
muscovite  in  the  eruptive  rocks.  It  is  found  in  most  of  the  muscovite  localities,  and 
is  a  very  common  constituent  of  rocks  and  soils  in  the  form  of  small  scales.  It  alters 
more  readily  than  muscovite  to  chlorite  or  to  epidote,  quartz  and  iron  oxide. 

PHLOGOPITE.—  Amber  Mica,  Bronze  Mica. 

COMPOSITION.  —  R3Mg3Al(SiO4)3,  where  R  =  H,K,MgF. 

GENERAL  DESCRIPTION.  —  Large  and  small,  brownish-red  to 
nearly  black  crystals.  Usually  rough,  tapering,  six-sided  prisms. 
Thin  plates  sometimes  show  a  six-rayed  star  by  transmitted  light. 

Optically  — .  Axial  plane  parallel  to  b,  that  is  parallel  to  the 
principal  line  of  the  percussion  figure.  Axial  angle  small,  but 
varying  in  the  same  specimen.  Pleochroic  in  colored  varieties. 

Physical  Characters.     H.,  2.5  to  3.     Sp.  gr.,  2.78  to  2.85. 
LUSTRE,  pearly  or  submetallic.     TRANSPARENT  to  translucent. 
STREAK,  white.  TENACITY,  tough  and  elastic. 

COLOR,  yellowish-brown,  brownish-red,  green,  colorless. 
CLEAVAGE,  basal  eminent. 

BEFORE  BLOWPIPE,  ETC. — Whitens  and  fuses  on  thin  edges.  In 
closed  tube  yields  water.  Soluble  in  sulphuric  acid  with  separa- 
tion of  scales  of  silica. 

REMARKS. — Phlogopite  is  usually  found  in  crystalline  limestones  or  in  serpentine. 
It  occurs  in  enormous  crystals  in  Ontario  and  Quebec,  and  in  various  localities  through 
New  York  and  New  Jersey. 

USES.  —  It  is  largely  used  in  electrical  work  as  an  insulating 
material. 

CHLORITE.  —  Prochorite,  Clinochlore,  Ripidolite. 

COMPOSITION.  —  Silicates  of  iron,  magnesia  and  alumina  con- 
taining about  1 2  per  cent,  of  water. 

GENERAL  DESCRIPTION.  —  Dark-green  masses,  composed  of 
coarse  to  very  fine  scales.  Also  tabular  and  curiously  twisted  six- 
sided  crystals,  which  easily  cleave  into  thin  plates  which  are  soft 
and  pliable  but  not  elastic.  Also  frequently  distributed  as  a  pig- 
ment in  other  minerals. 
Physical  Characters.  H.,  i  to  2.5.  Sp.  gr.,  2.65  to  2.96. 

LUSTRE,  feebly  pearly.  TRANSLUCENT  to  opaque. 

STREAK,  white  or  greenish.      TENACITY,  flexible,  non-elastic. 

COLOR,  grass-green,  blackish-green  or  red. 

CLEAVAGE,  basal  perfect.          FEEL,  slightly  soapy. 


420  DESCRIPTIVE  MINERALOGY. 

BEFORE  BLOWPIPE,  ETC.  —  Whitens  and  then  fuses,  varying 
from  easy  fusion  to  black  magnetic  glass  to  difficult  fusion  to  a 
yellow  enamel.  In  closed  tube  yields  water  at  a  high  heat.  Sol- 
uble in  sulphuric  acid,  only  slightly  in  hydrochloric  acid. 

REMARKS.  —  Formed  by  decomposition  of  mica  and  aluminous  varieties  of  amphi- 
bole,  garnet,  pyroxene  and  feldspars,  and  occasionally  found  as  an  earthy  substance  in 
cavities  of  crystalline  schists  and  serpentines. 


Delessite,  a  dark-green  massive  mineral  of  scaly  or  short  fibrous  appearance.  H., 
2.5.  Sp.  gr.,  2.9.  It  yields  water  in  the  closed  tube  and  is  decomposed  by  HC1  with 
separation  of  silica.  Found  in  cavities  of  amygdaloidal  eruptive  rocks. 


SERPENTINE  AND  TALC  DIVISION. 

SERPENTINE. 

COMPOSITION. — H4Mg3Si2O9,  with  replacement  by  Fe. 

GENERAL  DESCRIPTION. — Fine  granular  masses  or  microscop- 
ically fibrous.  Also  foliated  and  coarse  or  fine  fibrous.  Color, 
green,  yellow  or  black,  and  usually  of  several  tints  dotted,  striped 
and  clouded.  Very  feeble,  somewhat  greasy  lustre  and  greasy 
feel.  Crystals  unknown. 

Physical  Characters.     H.,  2.5  to  4.,  Sp.  gr.,  2.5  to  2.65. 
LUSTRE,  greasy,  waxy  or  silky.  TRANSLUCENT  to  opaque. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  green  to  yellow,  brown,  red,  black,  variegated. 

BEFORE  BLOWPIPE,  ETC. — Fuses  on  edges.  In  closed  tube, 
yields  water.  In  cobalt  solution  becomes  pink.  Soluble  in  hy- 
drochloric acid,  with  a  residue. 

REMARKS. — A  secondary  mineral  formed  from  chrysolite,  amphibole,  pyroxene, 
enstatite,  etc.  It  is  associated  with  these  and  with  magnetite,  garnierite,  chromite, 
dolomite,  etc.  Serpentine  asbestus  is  not  produced  in  the  United  States,  but  large 
amounts  are  annually  imported  from  the  Thetford  and  Coleraine  mines  of  Quebec. 
Massive  serpentine,  or  Verd  Antique  marble,  is  quarried  at  Milford,  Conn. 

USES. It  takes  a  fine  polish,  and  is  used  for  ornamental  work, 

as  table-tops,  mantels,  etc.    The  fibrous  variety,  chrysotile,  is  used 
as  asbestus. 


SILICA   AND    THE  SILICATES.  421 

TALC.— Steatite,  Soapstone. 

COMPOSITION.— H2Mg3(SiO3)4. 

GENERAL  DESCRIPTION. — A  soft,  soapy  material,  occurring  foli- 
ated, massive,  and  fibrous,  with  somewhat  varying  hardness.  Usu- 
ally white,  greenish  or  gray  in  color.  Crystals  almost  un- 
known. 

Physical    Characters.     H.,  I.     Sp.  gr.,  2.55  to  2.87. 
LUSTRE,  pearly  or  wax-like.  TRANSLUCENT. 

STREAK,  white.  TENACITY,  sectile. 

COLOR,  white,  greenish,  gray,  brown,  red. 
CLEAVAGE,  into  non-elastic  plates.  FEEL,  greasy. 

BEFORE  BLOWPIPE,  ETC. — Splits  and  fuses  on  thin  edges  to  white 
enamel.  With  cobalt  solution,  becomes  pale  pink.  Insoluble  in 
acid. 

VARIETIES. 

Foliated  Talc. — H  =  I.  White  or  green  in  color.  Cleavable 
into  non-elastic  plates. 

Soapstone  or  Steatite. — Coarse  or  fine,  gray  to  green,  granular 
masses.  H.,  1.5  to  2.5. 

French  Chalk. — Soft,  compact  masses,  which  will  mark  cloth. 

Agolite. — Fibrous  masses  of  H.  3  to  4. 

Rensselaerite. — Wax-like  masses.  H.,  3  to  4.  Pseudomorphous 
after  pyroxene. 

SIMILAR  SPECIES. — Softer  than  micas  or  brucite  or  gypsum. 
Further  differentiated  by  greater  infusibility,  greasy  feel,  and  the 
flesh-color  obtained  with  cobalt  solution. 

REMARKS. — Talc  is  an  alteration  product  of  pyroxene,  amphibole,  muscovite,  ensta- 
tite,  etc.,  and  occurs  with  dolomite,  serpentine,  magnesite,  tourmaline,  etc.  An  im- 
mense deposit  at  Gouverneur,  N.  Y.,  is  mined,  and  the  total  output  is  ground  for  use 
in  paper-making,  etc.  Large  soapstone  quarries  are  worked  at  Francestown,  N.  H. 
Chester,  Saxon's  River,  Cambridgeport  and  Perkinsville,  Vt.,  Cooptown,  Md.,  and 
Webster,  N.  C.  Massachusetts,  New  Jersey,  Pennsylvania,  Virginia  and  Georgia  are 
also  producing  States. 

USES. — Soapstone  is  cut  in  slabs  for  hearths,  linings  of  stoves, 
sinks  and  other  articles  of  refractory  nature.  It  is  ground  and 
moulded  into  gas-tips,  and  used  as  a  preparation  for  blackboards 
and  as  a  fine  quality  of  tinted  plastering.  Agolite  is  used  to  mix 


422  DESCRIPTIVE  MINERALOGY. 

with  wood  pulp  in  paper  manufacture.  Talc  is  used  in  soap,  as  a 
dressing  for  fine  skin  and  leather,  as  a  lubricant  and  as  pencils, 
tailors'  chalk,  etc. 

SEPIOLITE.— Meerschaum. 

COMPOSITION. — H4Mg2Si3O,0. 

GENERAL  DESCRIPTION. — Soft  compact  white,  earthy  to  clay- 
like  masses,  of  very  light  weight.  Rarely  fibrous. 

Physical  Characters.     H.,  2  to  2.5.     Sp.  gr.,  i  to  2. 
LUSTRE,  dull.  OPAQUE. 

STREAK,  white.  TENACITY,  brittle. 

COLOR,  white,  gray,  rarely  bluish-green.        FEEL,  smooth. 

BEFORE  BLOWPIPE,  ETC. — Blackens,  yields  odor  of  burning  and 
fuses  on  thin  edges.  In  closed  tube  yields  water.  With  cobalt 
solution  becomes  pink.  In  hydrochloric  acid  gelatinizes. 

SIMILAR  SPECIES. — Resembles  chalk,  kaolinite,  etc.,  but  is 
characterized  by  lightness  and  gelatinization  with  acids. 

REMARKS. — Possibly  formed  from  Magnesite.  The  name  "meerschaum"  refers  to 
the  fact  that  it  will  float  on  water  when  dry.  Most  of  the  material  used  for  pipes  is 
obtained  from  Turkey.  It  occurs  in  large  amount  in  Spain,  and  in  smaller  quantities 
in  Greece,  Morocco  and  Moravia.  There  are  no  productive  American  localities. 

USES. — As  material  for  costly  tobacco  pipes.  In  Spain  it  is  a 
building  stone,  In  Algeria  it  is  used  as  a  soap. 


KAOLINITE  —Kaolin,  China  Clay. 

COMPOSITION.  H4Al2Si2O9,  with  more  or  less  iron,  silica,  and 
organic  matter. 

GENERAL  DESCRIPTION. — Compact  and  clay-like  or  loose  and 
mealy  masses  of  pure  white,  yellow,  brown,  red  and  blue  color. 
Also  in  white,  scale-like  crystals,  with  the  lustre  of  satin.  Usually 
unctuous  and  plastic. 

Physical  Characters.     H.,  2  to  2.5.     Sp.  gr.,  2.6  to  2.63. 
LUSTRE,  dull  or  pearly.  OPAQUE  or  translucent. 

STREAK,  white  or  yellowish.  TENACITY,  brittle. 

COLOR,  white,  yellow,  brown,  red  and  blue. 


SILICA   AND    THE  SILICATES. 


423 


BEFORE  BLOWPIPE,  ETC. — Infusible.  Yields  water  in  closed 
tube.  With  cobalt  solution,  becomes  deep  blue.  Decomposed 
by  sulphuric  acid,  but  insoluble  in  nitric  or  hydrochloric  acids. 

SIMILAR  SPECIES. — It  is  not  harsh  like  infusorial  earth  and  is 
softer  than  bauxite. 

REMARKS. — Kaolinite  is  formed  by  alteration  of  feldspars  and  other  silicates. 
Carbonated  waters  remove  the  basic  oxides  and  part  of  the  silica.  Its  associates  are 
feldspars,  corundum,  diaspore,  topaz,  etc.  In  the  United  States  kaolinite  is  mined  at 
Okahumka,  Lake  County,  Florida,  at  Sylva,  Dilsboro  and  Webster,  N.  C.,  and  at  sev- 
eral places  in  New  Castle  County,  Del,  and  Chester  and  Delaware  Counties,  Pa. 
Kaolin  of  poorer  quality  is  obtained  in  Ohio  and  New  Jersey,  and  many  other  de- 
posits are  known  throughout  the  Atlantic  States. 

USES- — It  is  the  chief  constituent  of  porcelain,  chinaware,  orna- 
mental tiles,  etc. 

FIG.  579. 


Pyrophyllite,  Lincoln  Co.,  Ga.     N.  Y.  State  Museum. 

PYROPHYLLITE.— Pencil  Stone. 

COMPOSITION.— HAl(SiO3)2. 

GENERAL  DESCRIPTION.— Radiated  Mix  or  fibres  and  compact  masses  of  soapy- 
feeling  and  soft  and  smooth  like  talc. 

PHYSICAL  CHARACTERS.— Translucent  to  opaque.  Lustre,  pearly  or  dull.  Color, 
white,  greenish,  brownish  or  yellow.  Streak,  white.  H.,  I  to  2.  Sp.  gr.,  2.8  to  2.9. 
Flexible. 

BEFORE  BLOWPIPE,  ETC.— Whitens  and  fuses  on  the  edges,  and  often  swells  and 
spreads  like  a  fan.  In  closed  tube  yields  water.  Partially  soluble  in  sulphuric  acid. 

REMARKS.— Occurs  in  large  beds  and  as  gangue  of  cyanite. 


424  DESCRIPTIVE  MINERALOGY. 

USES. — Extensively  manufactured  into  slate  pencils. 

TITANO-SILICATES. 
TITANITE.  —  Sphene. 

COMPOSITION.  —  CaSiTiO5. 

GENERAL  DESCRIPTION.  —  Brown,  green  or  yellow,  wedge-shaped 
or  tabular  monoclinic  crystals,  with  adamantine  or  resinous  lustre. 
Also  compact,  massive.  Rarely  lamellar. 

CRYSTALLIZATION.  —  Monoclinic.    /?  =  60°  FlG-  580. 

17'.  Axes  a  \~&\c  =  0.755  :  l  :  0.854.  Crys- 
tals very  varied.  The  most  common  forms 
are :  pinacoids  c  and  a,  unit  prism  ;;/,  negative 
unit  pyramid  /,  domes  x  =  (a  :  co  ~t>  :  }4c); 
{102},  and  s  =  (co  a  :  1  :  2c);  {021},  and  the  Diana>  N  Y 

pyramid  l=(a:b:  fa) ;  {112}.  Supplement 
angles  are :  mm  =  66°  29'  ;  pp  =  43°  49'  ;  //  =  46°  f. 

Optically  +.  Axial  plane  the  plane  of  symmetry.  Very  large 
dispersion  producing  peculiar  interference  figure  with  many  lem- 
niscates  and  colored  hyperbolae. 

Physical  Characters.     H.,  5  to  5.5.     Sp.  gr.,  3.4  to  3.56. 
LUSTRE,  adamantine  or  resinous.        TRANSPARENT  to  opaque. 
STREAK,  white.  TENACITY,  brittle. 

COLOR,  brown  to  black,  yellow,  green,  rarely  rose-red. 
CLEAVAGE,  prismatic  easily,  pyramidal  less  easily. 

BEFORE  BLOWPIPE,  ETC. — Fuses,  with  intumescence,  to  a  dark 
glass,  sometimes  becoming  yellow  before  fusion.  In  salt  of  phos- 
phorus after  reduction,  the  bead  is  violet.  Partly  soluble  in 
hydrochloric  acid,  completely  so  in  sulphuric  acid. 

REMARKS. — Occurs  both  as  original  and  secondary  mineral  derived  from  alteration 
of  menaccanite,  brookite,  etc.  Its  associates  are  pyroxene,  amphibole,  feldspars,  zir- 
con, iron  ores,  apatite,  etc.  Good  gem  stones  have  been  found  at  Brewsters,  N.  Y.; 
Bridgewater,  Pa.,  and  Magnet  Cove,  Ark. 

USES. — As  a  gem. 


PART  IV. 


DETERMINATIVE   MINERALOGY. 


CHAPTER   XXXVII. 

TABLES    FOR  RAPID    DETERMINATION   OF   THE    COMMON 
MINERALS. 

IN  the  tables  which  follow,  the  minerals  are  divided  first  into 
minerals  of  metallic  lustre  and  minerals  of  non-metallic  lustre. 
The  minerals  of  metallic  lustre  are  divided  into  forty -eight  groups 
by  eight  horizontal  divisions,  based  on  color  and  hardness,  and  six 
vertical  divisions  based  on  the  effect  of  the  blowpipe  flame  on 
charcoal. 

From  the  minerals  of  non-metallic  lustre  a  division,  A,  of  min- 
erals possessing  a  taste,  that  is,  soluble  in  water,  is  set  aside.  The 
non-metallic  minerals  without  taste,  as  Division  B  and  C,  are  then 
divided  into  forty-four  groups,  the  action  of  hydrochloric  acid 
giving,  in  each,  four  horizontal  divisions,  and  the  action  upon  char- 
coal, in  B,  and  in  the  platinum  forceps,  in  C,  giving  the  vertical 
divisions. 

The  species  in  each  group  are  printed  in  heavy  type  or  ordinary 
type,  according  to  their  importance.  The  symbols  I.,  T.,  H.,  O., 
M.,  Tri.  before  each  name  designate  the  system  of  crystallization. 
The  formula  following  is  expected  to  suggest  confirmatory  blow- 
pipe tests  and  the  lines  of  fine  type  to  suggest  distinctive  test  or 
characters.  H  signifies  hardness,  G,  specific  gravity,  S.  Ph.,  salt 
of  phosphorus.  The  page  reference  to  the  complete  description  of 
the  species  is  also  given. 

For  accurate  results  these  precautions  must  be  taken  : 

i.  All  tests  should  be  made  upon  homogeneous  material,  prefer- 
ably crystalline,  as  the  tests  may  be  unreliable  if  the  material  is 
impure,  unless  the  effect  of  the  impurity  upon  the  test  is  known. 

425 


426  DETERMINATIVE  MINERALOGY. 

2.  The  classifying  tests  must  be  decided,  and,  if  weak,  should  be 
attributed  either  to  improper  manipulation  or  to  the  presence  of 
some  accidental  impurity. 

3.  The  lustre  must  be  observed  on  a  fresh  fracture. 

4.  The  determination  must  be  confirmed  by  reference  to  the 
description  of  the  species,  and,  when  possible,  by  comparison  with 
known  specimens. 

5.  When  the  test  is  very  close  to  a  line  of  division  it  is  better  to 
look  for  the  mineral  upon  both  sides  of  the  line. 

If,  as  may  happen,  a  specimen  belongs  to  a  rare  species  not  in- 
cluded in  the  scheme,  its  tests  and  description  will  not  correspond 
to  any  species  therein  and  more  elaborate  tables  will  be  needed. 


TABLE   I.-MINERALS  OF  META 
The  Mineral  He; 


GIVES  GARLIC  ODOR. 

GIVES  WHITE  COATING  BUT  NO 
GAELIC  ODOR. 

GIVES  YELLOW  COATING  X 
THE  ASSAY  ON  CONTINUED  B 

>• 

i 

s 

Z  o 

:H.  Molybdenite,  p.  278,  MoS, 
Soapy  feel.    Streak  greenish. 
0.  Stibnite,  p.  273,  Sb2S3 
Easy  fusion.     Dark-gray  color. 

-  Lead,  p.  256,  Pb 
H.  Tetradymite,  p.  268,  Bi2(T 
Bluish-green  flame. 
O.  Bismuthinite,  p.  268,  Bi2S3 

1 

i 

Distinctly  Scr 
by  Calcit 

Blue-green  flame. 
GoldTelluride,p.306,(Au,Ag)Te2 
Residue  yellow.       White  subli- 
mate is  made  rose  by  H2SOt 
H.  Tellurium,  p.  361,Te.  No  residue. 
I.  Hessite,  p.  298,  Ag,Te 
Residue  white  (silver). 

Needles  or  masses.    G  =  6.4 
O.  Jamesonite,  p.  259,  Pb.,SbaS 
Fibres  or  needles.    G  ="5.5  t 
H.  Bismuth,  p.  267,  Bi.  Arbor 
0.  Aikinite.p.  268,  PbCuBiS3 
Embedded  prisms  or  massiv 
I.  Galenite,  p.  256,  PbS 
Cubic  cleavage.    G  =  7.4  to  " 

& 

Distinctly 
Scratched 
by  a 
Knife. 

H.  Arsenic,  p.  270,  As 
Brittle.    Blue  flame. 
H.  Antimony,  p.  273,  Sb 
Thick  fumes.    Green  flame. 
I.  Tetrahedrite,  p.  286,  Cu.SbaST 
See  opposite. 

H.  Antimony,  p.  273,  Sb                     |o.  Bournonite,  p.  258,  CuPbSb 
Brittle.    Thick  fumes.                        Simple  and  cog-wheel  crysta 
I.  Stannite,  p.  249,  (Cu,Sn,Fe)S             G  =  5.7  to  5.9. 
Coat  blue  by  cobalt  solution.          ,1.  Clausthalite,  p.  259,  PbSe 
I.  Tetrahedrite,  p.  286,  Cu8Sb2S7      Odor  of  horse-radish. 
Black  Streak.    Color  dark  gray. 

to 

In  closed  tube. 

S 

£      .    ;O.  Leucopyrite  p.  215,  Fe3As4 
0<2<JJ         Black  sublimate. 

0 

.S  J5  "3     I.  Cobaltite,  p.  234,CoAsS,  unalt'd. 

o 

«2«     I.  Smaltite,  p.  235,  (Co,Ni)Ass 
5  g  eg         Black  sublimate. 

XJ 

"  £  >,     I.  Chloanthite,  p.  236,  (Ni,Co)As, 

Black  sublimate. 

* 

0.  Arsenopyrite.  p.  214,  FeAsS 
Red  sublimate,  then  black. 

A 

O.  Stibnite,  p.  273,  Sb2S3 
Very  ensy  fusion. 
o.  Stephanite,  p.  300,  Ag£SbS4 
Black  streak.    Fuses  leaving  Ag. 

I.  Galenite,  P.  256,  PbS 
Cubic  cleavage.    G  =  7.4  to  ' 

"**  "5  J£ 

M.  Polvbasite,  p.  301,  (Ag.CuJjSbS. 

• 

.2  a  * 

Black  streak.    Cu  with  S.Ph. 

§ 

°i 

H.  Pyrargyrite,  P.  299,  Ag3SbSs 
Purplish-red  streak. 

*    r?«,2 

O.  Enargite,  p.  286,  Cu3AsS4 
Columnar. 

I.  Tetrahedrite,  p.  286,  Cu.sbgsT 
Tetrahedral  or  fine-grained. 

J3     .£S£'S       I.  Tennantite,  p.  288,  Cu.As,ST 

I.  Sphalerite,  P.  242,  ZnS 

O  ;  Q  w     M    Granular. 

Pale-brown  streak. 

8 

i 

I.  Franklinite,  p.  217, 
(FeMnZn).O4 
Brown-streak.  White  coat. 

I.  Uraninite,  P.  276,  u.Pb.Tt 

Botryoidal.    Green  bead  .S.  I 
R.F. 

H 

J5 

1 

1 

z 

S 

• 

H.  Niccolite,  p.  239,  NiAs 
Color,  copper-red.    Streak  black. 

O.  Gold  Telluride,  p.  306, 
(AgAu)Tea.    Color  brass-yellow. 

I 

III 

I 

Not 
S'dby 
Knife. 

C  OR  SUBMETALLIC  LUSTRE. 

I  on  Charcoal : 


GIVES  MAGNETIC  RESIDUE  BUT 
NO  COATING  OB  GARLIC 
ODOR. 

GIVES  NON-MAONETIC  METAL 
BUT  NO  COATING  OH 
GARLIC  ODOR. 

NOT  PREVIOUSLY  INCLUDED. 

0.  Stromeyerite,  p.  298,  (Ag,Cu),S 
I.  Amalgam,  p.  298,  Agkg 
Whiten,  copper. 

—  .  Mercury,  p.  293,  Hg. 
Fluid  globules.    Entirely  volatilized. 

I.  Platinum,  p.  308,  Pt(Fe) 
Grains  and  scales.    G.  14  to  19. 
I.  Iron,  p.  208,  Fe. 
Grains  and  masses.     G.  7.3  to  7.8. 

L  Silver,  p.  2%,  Ag 
Malleable.    Silver  streak. 
Q  =  10  to  11. 
I.  Platinum,  p.  308,  Pt 
Grains  and  scales.    G  =  14  to  19. 

I.  LinnsBite,  p.  233,  (Co,Ni)3S4 
Octahedrons  or  massive. 

H.  Iridosmine,  p.  308,  (Ir.Os) 
Flat  grains.    H  =  6  —  7. 

I.  Argentite,  p.  297,  Ag,S 
Sectile.    Residue  of  silver. 
M.  Tenorite,  p.  289,  CuO 
Minute  scales  or  earthy  masses. 

H.  Graphite,  p.  368,  C 
Soapy  feel.    Shining  streak. 
O.  Pyrolusite,  p.  229,  MnO. 
Radiating  or  compact.     Black  streak. 
Scratched  by  finger  nail. 

0.  Chalcocite,  P.  283,  Cu2S 
Brittle.    Residue  of  copper. 

I.  Alabandite,  p.  228,  MnS 
Cubic  cleavage.    Green  streak. 
0.  Manganite,  p.  230,  MnO(OH) 
Prismatic.    Dark-brown  streak. 

-,  Turgite,  p.  220,  Fe«O5  (OH), 
Red  Streak.     Decrepitates. 
O.  Goethite,  p.  220,  FeO(OH) 
Yellow  streak.    Crystalline. 
-,  Limonite,  Fe3O:!,Fe,(OH)« 
Yellowish-brown  streak,  n.  221. 
M.  Wolframite,  (Fe.Mn)fto4 
Fuses  easily.  G=7.2  to  7.5,  p.  225. 
II.  Hematite,  p.  217,  Fe,O, 
Red  streak.     Brilliant  lustre. 
H.  Ilmenite.  p.  219,  (Fe.MrJOTiO, 
Red  or  black  streak.   Violet  S.  Ph. 
inR.  F. 
I.  Magnetite,  p.  215,  Fe3O4 
Black  streak.    Magnetic. 
I.  Franklinite,  (I  •>MuZn).O4 
Brown  streak.    White  coat,  p.  217. 
I.  Cnromite,  P.  224,  FeCr,O« 
Brown  streak.    Green  in  S.  Ph. 

O.  Columbite,  p.  225.  Fe(CbOs), 
Brilliant  lustre.     G  =  5.3  to  7.3. 
I.  Uraninite,  P.  276.  U.Pb.Th,  ete. 
Botryoidal.     Green  S.Ph.  in  R.F. 
-.  Psilomelane,  P.  231,  H4MnO, 
Botryoidal.    Brownish-black  streak. 
T.  Hausmannite.  p.  229,  Mn3O. 
Twin  pyramids.     Chestnut-brown 
streak. 
T.  Braunite,  Mn2O3.MnSiO, 
Black  streak.     Gelatinizes,  p.  228. 
T.  Rutile,  p.  251,  TiO, 
Violet  bead  S.Ph.  in  R.F. 
0.  Brookite,  p.  252,  TiOs 
l.  Cnromite,  p.  224,  FeCr,O« 
Brown  streak.    Green  in  S.Ph. 

I.  Bornite,  p.  284,  Cu.FeS* 
Red-bronze  fracture. 
H.  Millerite.  p.  238,  NiS 
Brassy  needles  or  hair. 
I.  Pentiandite,  p.  238,  (Fe,Ni)S 
Light  bronze-yellow. 
T.  Chalcopyrite,  p.  284,  CuFeS, 
Deep  brass-yellow. 
H.  Pyrrhotite,  P.  209,  FenSn+i 
Brown-yellow.    Magnetic. 

I.  Gold,  p.  304.  (Au.Ag) 
Golden  streak.    Malleable. 
I.  Copper,  P.  282,  Cu 
Copper  streak.    Malleable. 
I.  Cuprite,  P.  288,  Cu,O 
Brownish-red  streak.    Brittle. 

I.  Pyrite,  P.  210,  FeS, 
0.  Btarcasite,  p.  212,  FeS4 

TABLE  I!.— MINERALS  O 
A.    Minerals  with  Decided  ' 


NAME. 

TASTE. 

IN  THE  FORCEPS 
O.  F.  THE  FLAME  is 
COLORED. 

Tri.  Sassolite,  p.  35G,  H3BO, 
M.  Mirabilite,  p.  314,  Na2SO<  +1011,0 
0.  Mascagnite,  p.  318,  (NH4)2SO4 
O.  Epsomite,  p.  340,  Mgt>O4+7H2O 
H.  Aphthitalite,  p.  311,  (K.Ka).SO4 
M.  Borax,  p.  S3C,  Na2B4O7-rlO~H.,O 

Acid,  slightly  saline. 
Bitter,  cooling. 
Bitter,  pungent. 
Bitter  and  salt. 
Bitter  and  salt. 
Alkaline,  sweetish. 

Yellowish  green. 
Yellow. 

Violet. 
Yellow. 

M.  Trona,  p.  315,  Xa2CO3.NaHCO3  +  2H,O 
M.  Alunogen,  p.  351,  A12(SO4)3+18H,O 
M.  Melanterite,  p.  223,  FeSO47H,O 
O.  Goslarite,  p.  242,  ZnSO4+7H2O 
L  Kaliiiite,  p.  311,  KAl(SO4),-f  12HZO 

Alkaline. 
Astringent 
Astringent  sweetish. 
Astringent  nauseous. 
Astringent 

Yellow. 
Violet. 

Tri.  Chalcanthite,  p.  289,  CuSO4+5H_O                             Astringent  nauseous.                       Kmerald  green. 
M.  Copiapite,  p.  222,  Fe2Fe(OH)a(S04)s18H20              Astringent   nauseous. 
H.  Soda  Nitre,  p.  314,  NaNO3                                         Saline,  cooling.                                Yellow. 

I.  Sal  Ammoniac,  p.  318,  NH4C1                                          Saline. 

O.  Nitre  p.  311   KNO3                                                        Saline,  cooling. 

Violet. 

I.  Sylvite,  p.  310,  KC1  or  Carnallite  KCl.MgC1.6H2O          Saline. 

Violet. 

O.  Thenardite,  p.  314,  Na2SO4                                             Saline. 

Yellow. 

I.  Halite,  p.  312.  NaCl                                                         Saline. 

Yellow. 

M.  Glauberite,  p.  314,  Na.2SO4CaSO4 
M.  Kainite,  p.  310,  MgSO4KCl+3H2O 

Saline. 
Saline. 

Yellow. 
Violet. 

B.    The  Mineral  is  Without  Taste,  but  stron 


*; 

YIELDS  ARSENICAL  ODOR. 

YIELDS  WHITE  COATING  BUT  NO 
ARSENICAL  ODOR. 

YIELDS  ^ 

il 

J£ 

—  .  Hydrozincite,  p.  244,  Zn3CO3(OH)4         O.  Cerussit 
H.  2  to  2.5.    Chalkv  or  pearly.                        Greenish  ve 
T.  Phosgenite,  p.  263,  (PbCl)2CO,                   -.  Bismutite 
Yellow  coat  with  Bi  flux.                                 Chocolate  an 

•£ 

2 

I.  Sphalerite,  p.  242,  ZnS 

X 

8 

Evolution  H2S.    Brown  to  black  color. 

1 

H.  Smithsonite,  P.  244,  ZnCO3 
H.  5.  Vitreous,  botryoidal,  drusy. 

*    21* 

0.  Calamine,  p.  246,  (ZnOH).,SiOj 

\\aterinclosedtube. 

•S     Qfc^ 

JH.  Willemite,  p.  245,  Zn,Si04  Anhydrous. 

| 

without  Effervescence 
mation  of  Jelly. 

Magnetic  Residue. 
M.  Annabergite,  p.  239,  Nis(AsO4)1+8H.iO 
Apple  green  crusts  or  fibers. 
M.  Erythrite,  p.  236,  Cos(AsO4)2+8H20 
Crimson  fibers  and  prisms. 

Non-Magnetic  Residue. 
H.  Mimetite,  p.  262,  Pb6Cl(AsO4)3 
Prisms  or  globular  groups. 
0.  Olivenite,  p.  290,  Cu^OHlAsO. 
Olive  green  to  brown  crystals  and  fibers. 

O.  Valentinite,  p.  275,  Sb2O, 
White  silky  prisms  or  fibers. 
I.  Senarmonite,  p.  275,  Sb2O, 
Pearl  gray  octahedrons. 
M.  Kermesite,  p.  275,  Sb2S,O 
Cherry  red  tufts  or  fibers. 
O.  Molybdite,  p.  278,  MoOs 
Yellow  powder,  usually. 
H.  Zincite,  p.  243,  ZnO 
Dark  red,  cleavable  or  grains. 
O.  Atacamite,  p.  289,  Cu2(OH)sCl 
Deep  emerald  green. 

—  .  Bismite,  j 
Yellow  to  w 
—  .  Minium, 
Vivid  red  pr 
M.  Crocoite, 
Hyacinth  re 
H.  Pyromoi 
Green  or  brc 
H.  Vanadin 
Red  or  brow 
0.  Descloizit 
Drusv.     Bla 

P^         73  o 

Blue  flame  mixed  with  green. 

T.  Wulfenit 

1  i' 

Yellow  or  br 

5  " 

_ 

i 

soluble  or 
f  Insoluble. 

H.  Proustite,  p.  299,  Ag3AsS3                    H.  Pyrargyrite,  p.  299,  Ag,SbS3 
Color  and  streak  scarlet  vermilion.                Color  nearly  black,  streak  purplish  red. 
O.  Orpiment,  p.  271,  As2S3                           T.  Calomel,  p.  294,  Hg,Cl, 
Color  and  streak  lemon  yellow.                       Completely  volatilized 
M.  Realgar,  p.  271,  AsS 
Streak  orange  red,  color  darker. 

O.  Anglesit 
Colorless  to 
M.  Linarite, 
Deep  blue  cr 

Si 

j 

Z 

MOM-METALLIC   LUSTRE, 
te,  that  is,  Soluble  in  Water. 


FLAME  is  NOT  COLORED. 
BATED  ON  COAL  THE 
MINERAL  : 

HARDNESS. 

REMARKS. 

1.5  to  2 

White  pearly  scales,  smooth  feel. 
White  efflorescent  crusts. 

ields  white  fumes, 
elts,  becomes  infusible. 

2  to  2.5 
2  to  2.5 

Gray  mealy  crusts  and  stalactites. 
White  massive  or  silky  fibers. 

3  to  3.5 

Delicate  crystals  on  lava,  or  crusts. 

2  to  2.5 
2.5  to  3 

White  crystals  resembling  those  of  pyroxene,  or  crust*. 
White  glistening  crusts  or  beds. 

elts,  becomes  infusible.                     1.5 

White  silky  fibers  or  crusts. 

ecomes  magnetic.                                  2 
ields  white  fumes.                           2  to  2.5 

Pale  green  efflorescence  on  sulphide  of  iron. 
White  alteration  on  or  near  sphalerite. 

2  to  2.5 

White  efflorescence  on  clay  minerals. 

2.5 

Blue  crystals  or  masses. 

ecomes  magnetic. 

2.5 
1.5  to  2 

Yellow  scales  or  granular  masses. 
Deliquescent  crusts. 

ields  white  fumes. 

1.5  to  2 

White  crystals  or  incrusting. 

2 
2  to  3 

Acicular  crystals  or  tufts.    Not  altered  by  exposure. 
Colorless  cubes  or  white  masses. 

2  to  3 
2.5 

White  crossed  and  simple  crystals. 
White  or  brown  cubes  or  masses. 

2.5  to  3 
2.5  to  3 

Gray  tabular  crystals.     Efflorescence  on  long  exposure. 
White  to  red  granular  masses. 

heated  on  Charcoal  in  the  Reducing  Flame: 


w  COATING  BUT  NO 
ICAL  ODOR. 

VOLATILIZES,  NOT  PREVIOUSLY 
INCLUDED. 

YIELDS  MAGNETIC  RESIDUE  BUT  is 
NON-VOLATILE. 

62,  PbCO3 
oat  with  Bi  flux. 
9,  BiO.Bi(OH)2C03 
coat  with  Bi  flux. 

H.  Greenockite.  p.  247,  CdS 
Iridescent  tarnish  on  coal. 

H  Siderite,  p.  226,  FeCO3 
Sp.  Gr.  3.8  to  3.9.    Brown. 
H.  Ankerite,  p.  337,  (Ca,Mg,Fe)CO, 
Sp.  Gr.  2.9  to  3.1.    Grav  to  brown. 
H.  Rhodochrosite,  p.  '231,  MnCO, 
Sp.  Gr.  3.3  to  3.6.    Pink  to  red. 

M.  Allanite,  p.  408,  R",R3(Si04), 

Bi.O3 

9wder  or  mass. 
Pb3O4 

,  PbCrO4 
tals,  orange  streak. 
5.  p.260,  Pb5Cl(P04)3 
[•isms,  often  parallel. 
.  264,  Pb6Cl(VO4)3 
ms,  often  hollow. 
55,  (Pb,Zn)(PbOH)VO4 
own  or  red. 
>65,  PbMoO4 
uare  piates  or  pyramids. 

-.  Oarnierite,  P.  240,  H^Ni.MgjsiO.+H.o 

Deep  green  to  pale  green.    Soft  and  friable. 
O.  Hypersthene.  p.  384,  (Mg,Fe)SiO, 
Foliated,  metalloidal. 
M.  Vivianite,  p.  223,  Fe3(PO4)4+8H,O 
Blue  color  and  streak. 

Streak  yellow  to  brown. 
-.  Limonite,  P.  221,  Fe2O,.Fe4(OH). 
Earthy  to  compact  or  fibrous. 
O.  Goethite,  p.  220,  FeO(OH) 
Needles,  scales  and  velvet  crusts. 

Streak  Red. 
Turgite,  p.  220,  Fe4O8(OH), 
In  closed  tube  flies  to  pieces. 
H.  Hematite,  P.  217,  Fe,O3 
In  closed  tube  unchanged. 

59,  PbSO4 
crystals  or  massive. 
[(PbCu)OH]1SO4 

0.  Sulphur,  p.  360,  S 
Burns  with  blue  flame  and  odor  SO, 
H.  Cinnabar,  P.  294,  HgS  volatilized. 
Fused  in  Matrass  with  KHS04 
I.  Cerargyrite,  p.  301,  AgCl 
Globule,  yellow  hot,  white  cold. 
I.  Embolite,  p.  302,  Ag(ClBr) 
I.  Bromyrite,  p.  302,  AgBr 
Globule  red  hot,  yellow  cold. 
H.  lodyrite,  p.  302,  Agl 
Violet  vapor,  globule  dark  red  hot 

M.  Biotite,  p.  418. 
Black  micaceous. 
M.  Chlorite,  P.  419,  H.FeMgAISi 
M.  Pyroxenes,  p.  385,  rich  in  iron. 
Angle  of  prism  87°  10'. 
M.  AmphibOles,  p.  389,  rich  in  iron. 
Angle  of  prism  124°  11'. 
I    Garnets,  p.  396,  Andradite,  Alinandite. 
M.  EpidOte,  Ca,(Al.]-e),(A10H)(Si04)3 
Green  grains,  fibers  or  crystmls.    P.  406. 

TABLE   II.-MINERALS  WI 
C.    If  the  Mineral  is  Tasteless,  Non-Volatile  and  not  Made  Mag 


FUSES  EASILY  TO  A  WHITE  GLASS 

FUSES  EASILY  TO  A  COLORLESS 

FUSES  EASILY  TO  A  Coix 

OR  ENAMEL. 

GLASS. 

GLASS  OR  ENAMEL. 

JS 

O.  Witherite,  p.  320,  BaCO3 

M.  Azurite,  Cu3(OH),(CO 

Is 
il 

Colors  flame  yellowish  green. 
M.  Gaylussite,  CaNa2(CO3)2+5H,O 
Intense  yellow  flame.    P.  315. 

Deep  blue  color.    P.  290. 
M.  Malachite,  Cu2(OH)2C 
Bright  green  color.    P.  29( 

£2 

H.  Cancrinite,  R(Na2C03)(SiO4) 

Is  Dissol 
Effervei 

Forms  a  jelly  on  heating.    P.  395. 

'o 

a 

M.  Pectolite,  p.  387,  HNa,Ca(SiO,), 
Radiating  splintery  fibers. 
O-  Thomsonite,  iNa,Ca)Al2Si2O. 
P.  416.                                   +§H,0 

M.  DatOlite.p.  405,Ca(BOH)SiO4 
Intumesces.    Green  flame. 
I.  Analcite,  NaAl(SiO3)2).H2O 
Quiet  fusion,  yellow  flame.  P.  415. 

E.  Mellilite,  Si,Al,Fe,Mg.Ni 
Fuses  with  intumescence  tx 
or  yellow  glass.    P.  402. 

o 

t 

<2  . 

M.  wollastonite,  p.  387,  CaSiO3 
T.  Apophyllite,  P.  413, 
Hl4K,Ca.(SiO,)ie9H,0 
Swells,  colors  flame  violet. 

0.  Natrolite,  p.  416,  Na3Al2Si3Olo 

Quiet  fusion.    Slender  prisms.  * 
H.  Nephelite.  Na8Ai8Si9o34 

o 

*r  *3 

H.  Chabazite,  P.  414, 

Strong  yellow  flame.     Glassy  or 

£ 

•o? 

(Ca,Na2iAl2(Si04)4+6H20 
Intumesces.    Nearly  cubic. 

with  greasy  luster.    P.  395. 

O 

> 

L  Hauynite,  p.  395, 

I  'i 

3(Xa2Ca)Al.SO4(SiO3)4 
Rounded  grains.    Sulphur  react. 

>»:  ^ 

L  Lazurite,  p.  396, 

•J 

Na4(NaS3Al)Al»(SiO4)3 
Intumesces.    Deep  blue  color. 

£ 

o 

M.  Cryolite,  p.  346,  AlNasF6 
Yellow  flame.    H  =  2.5. 

-.  Ulexite,  NaCaB.O.+8H20 
Yellow  flame.    H  =  1.    Silky. 

Flame  is  colored  blu 
O.  Atacamite,  p.  289,  Cu2(O 

> 

3 

T.  Wernerite,  Ca,Na,Al.SiO, 

P.  357. 

Deep  emerald  green. 

•c 

0 

i 

Effervescel 
3f  Jelly. 

Yellow  flame.    H  =  5  to  6.    P.  400. 
I.  Fluorite,  p.  325,  CaF2 
Red  flame.   Cubic,  phosphorescent. 
M.  Gypsum,  p.  328,  CaSO4+2H,O 
Pale  red  flame.    Water  test.    H=2. 
O.  Anhydrite,  p.  327,  CaSO4 

Tri.  Plagioclase,  (labradorite) 
p.  381.  NaAlSi3O,.nCaAl2Si2O, 
Partially  soluble.    H  =  6. 
M.  Colemanite,  Ca2B8o11J-5H2o 
Exfoliates.  Flame  green.  P.  357. 

Flame  is  colored  ernei 
green. 
0.  Libethenite,  p.  289,  Cu2(O 
Dark  to  olive  green  crysta 
O.  Brochantite,  CuSO43Cu(C 
Emerald  green  needle  cry 

Pale  red  flame.    H  =  3. 

P.  289. 

iT 
o 

I| 

I.  Boracite,  p.  359,  Mg7Cl2B18O30 
Green  flame.  Violet  by  Co  solution. 

I.  Cuprite,  p.  288,  Cu2O 
Deep  red  to  brownish  red. 

•o 

Is 

M.  Stilbite,  H4R,Al2(SiO3).+4H,O 
Sheaf-like.    Swells  with  heat. 

T.  Torbernite.  Pearly  green 
P.  277.    Ca(UO,).(70«),H 

1 

i 

:s  Dissolved 
or  Fo 

P.  414. 
M.  Heulandite,  p  414, 
H4CaAla(Si03)s+3HJO 
Swells  with  heat. 
0.  Prehnite,  H1Ca,Al2(SiO4), 
Usually  green.  H  =  6to6.5.  P.  408. 

Flame  not  colored 
0.  Autunite  Ca(UO2)2(P04) 
Pearlv  yellow  plates.     P. 

T.  Ves'uvianite,  P.  401, 
Ca^AKOH.FjJAL, 
0.  Prehnite,  P.  408. 

C 

il 

Tri.  Rhodonite,  p.  387,  MB 
Red,  fuses  black. 

c 

mfSSSSB8y.^Aijn-o.) 

Tri.  Plagioclase,  p.  381, 
vn       "(NaA1Si30.)CaAlaSi1108 

T.  Vesuvianite,  p.  401, 

Ca6(A10HF)Al2(S 

i 

M.  Petalite,  p.  378,  AlLi(Si2Os), 
Red  flame.    Phosphorescent. 

Yellow  flame.    H  =  6. 
M.  Spodumene.  LiAl(SiO3)2 
Red  flame.    Splits  in  thin  plates. 

Brown  to  bright  green  ~cr} 
and  columns. 
M.  Titanite,  p.  424,  CaSiT 

o 

G  =  2.4+ 

P.  316. 

Wedge-shaped  crystals 

c 

i 

u 

s 

3 
1 

Tri.  Amblygonite,  p.  316,  Li(  A1F)P04 
Intumesces.    Red  flame. 
O.  Celestite,  P.  321,  SrSO« 
Red  flame.    G  =  3.9-f 

M.  Pyroxene  (Diopside),  p.  385, 
CaMgSi2Os 
M.  Amphibole,  p.  389(Tremollte), 
CaMg3SUO12 

with  Sn  and  HC1  violet. 
M.  Epidote,Ca2Al2(A10H) 
Yellow  green  grains,  fibei 
crystals.     P.  406. 

I 

•  Nearly  In 

M.  Lepidolite,  p.  3i7,  R3Al(SiO,)s 
Red  flame.    Micaceous. 
0.  Barite,  p.  319,  BaSO4 
Green  flame.     G  =  4.3. 
O.  Zoisite,  Ca2(A10H)Al2(SiO4), 
Columnar.    No  flame.    P.  406. 

M.  Jadeite,  p.  386,  NaAlSi,O. 
Yellow  flame.    Compact. 
M.  Glaucophane,  p.  390, 
NaAl(SiO3)2(Fe,Mg)SiO, 
Yellow  flame.    Massive. 

I.  Garnet,  p.  396,  Spessarti 
MnsAJ.( 

andPvrope,  Mg,AU(Sif)4 
M.  Pyroxene,  (Ca,M"g,Fe)> 
Cleavage  and  prism  angle 

0 

• 

H.  Tourmaline,  RI3B2(SiOs)4 

P.  409. 

M.  Pyroxene,  p.  385,  RSiO3 
M.  Amphibole,  p.  389,  RSiO, 
H.  Beryl,  p.  391,  Be3Al,(SiO3). 

M.  Amphibole,  p.  389,  Acti 
Ca(Mg,Fe)3(t 
Cleavage  and  prism  angle 
Tri.  Axinite,H2R4(BO)AJ,( 
P.  408. 

5 

a 

Clove-brown,  acute  edged  cr 
H.  Tourmaline,  p.  409, 

H  =  7to7.5.  Hemimorphi 

OUT   METALLIC   LUSTRE. 

ic,  a  Fragment  is  Heated  in  the  Forceps  at  Tip  of  Blue  Flame. 


FUSES  WITH  DIFFICULTY. 

INFUSIBLE  BDT  IN  POWDER  MADE 
DKKP  BLUE  BY  COBALT  SOLUTION. 

INFUSIBLE,  NOT  INCLUDED 
PREVIOUSLY. 

M.  Barytocalcite,  p.  321,  (Ba.Ca)CO, 
Colors  flame  yellowish  greeu. 
O.  Strontianite,  p.  823,  SrCO, 
Colors  flame  crimson. 

H.  Magneslte,  p.  340,  MgCO, 
White  chalk-  like  masses. 
H.  Rhodochrosite,  p.  231,  MnCO, 
Pink  to  red. 

Red  Flame. 

H.  Calclte,  p  333,  CaCO3 
G.  2.71.    Rhonibohedral  cleavage. 
0.  Aragonite,  p  332,  CaCO3G=2.95. 
H.  Dolomite,  p.  335,  CaCO3.MgCO, 
Slow  effervescence  of  lumps. 

M.  Wollastonite,  p.  387,  CaSiO, 
Yellow-red  flame.    II  4.5  to  5 
Tri.  AnortMte,  p.  382,  CaAI2SisO, 
Yellow-red  flame.    H  6  to  6.5. 
—  .  Sepiolite,  p.  422,  H4Mg2h.i3O10 
Compact,  earthy.  Pink  with  cobalt 

O.  Calamine,  p.  246,  (ZnOH)2siO3 
White  coat  with  soda.    Water  in 
closed  tube. 
H.  Willemite,  p.  245,  ZnaSiO4 
White  coat  with  soda. 

T.  Thorite,  p.  254,  ThSi04 
H=5.    Orange  to  brown. 
H.  Dioptase,  p.  292,  HaCuSiO4 
H=5.    Emerald  green. 
O.  Chrysolite,  p.  398,  (Mg,Fe)aSiO4 
H=7.    Olive  to  gray-greeu. 
M.  Chondrodite,  H2Mg,,Si,O34F4 
H=6.5.    Brown  to  yellow.    P.  409. 

H.  Apatite,  p.  330,  Ca8(F,Cl)(P04)3 
Red  flame,  greeu  with  H»SO4 
T.  Scheelite,  p.  339,  Cawo4 
In  Ph.  S.  with  R.  F.  bead  blue 
when  cold. 
M.  Colemanite,  CajBeOn+SHjO 
Exfoliates.    Flame  green.  P.  357. 
-.  Serpentine,  P.  420,  H4Mg3SL(>9 
H=4.  Yields  water.  Lustre  greasy. 
O.  lolite,  H2(Mg,Fe)4AlBSilo03T 
H=7to7.5.    Blue  vitreous.    P.  394. 

M.  Aluminite,  p.  351,  Al.SO.j.SH.O 
H=l  to  2.    White  chalky  masses. 
—  .  Bauxite,  p.  346,  Alao(OH)4 
Oolitic  or  like  clay. 
O.  wavellite,  P.  352, 

Ale(OH)8(PO4)4  +  9HoO 
Spheres  and  hemispheres  of  radiat- 
ing crystals. 
—  .  Turquois,  A12(OH)3P04.H20 
Sky  blue  to  green  with  lustre  of 
wax.    P.  352. 
I.  Leucite,  P.  384,  KA1(Si03)a 
Trapezohedrons.     White   or   gray 
in  color. 

M.  Monazite,p.253,(Ce,La.I)i)(PO4) 
Resinous  brown  crystals  or  yellow 

H.  Brucite,  p  340,  Mg(OH)a 
Foliated  or  fibrous.    Pink  with  Co. 
solution. 
—  .  Wad,  p.  231,  Mn  oxides. 
Dull  earthy  brown  to  black. 
—  .  Chrysocolla,  CuSiOs+2H2O 
Green  to  sky-blue  with  waxy  lustre. 

0.  Talc,  p.  421,H,Mg3(Si03)4 
11=1.  Soapv.  Pink  with  Co  solution. 
—  .  Pyrophvllite,  p.  423,  HAl(SiO,), 
H=lto2.    Soapy.    Blue  by  Co  solu- 
tion. 

M.  CMorite,  p.  419, 
H(Mg,Fe)AlSiO 
H=lto2.5.    Dark  green. 
M.  MuscOvite,H.!(K,Na)Al3(SiO4)1 
H=25.  Light  colored  mica.  P.  417. 
M.  Phlogopite.  R3Mg3Al(SiO4), 
H=2.5.    Mica  in  limestone.   P.  419. 
M.  BiOtite,  p.  418, 
(KlF)2(Mg,Fe)2AI2(Si04)3 
H=2.5.     Dark  mica  in  granites. 
O.  Enstatite,  p.  384,  (Mg,Fe)SiO3 
i      H=5.5.     Foliated.    Pearly  lustre. 
M.  Orthoclase,  P.  378,  KAlSi3o. 
H=6.    Rectangular  cleavage. 
Tri.  Microcline,  p.  380,  KAlSi.O. 
H=6.    Striations  frequent. 
H.  Tourmaline,  B,,B2(SiO,)4 
H=7to7.5.   Hemimorphic.   P.  409. 
H.  Beryl,  p.  391,  Be3Al2(SiO3). 
H=7.5to8.    Prismatic. 

M.  Kaolinite,  P.  422,  H4AlaSiaO. 
H=2to2.5.    Soapy  feel. 
M.  Gibbsite,  p.  351,  Al(OH), 
H=2.5  to  3.5.    Clay  odor. 
H.  Alunite,  K(A103)(SO4)2  f3H.,O. 
H=3.5  to  4.    Small  white  cuboids 
P.  351. 
Tri.  Cyanite,  P  392,(AlO),Si03 
H=5.    Blue  bladed  crystals. 
O.  Sillimanite,  p.  405,  A1(A1O)SK>4 
H=6  to  7.    Gray  to  brown  crystals 
and  fibers. 
O.  Diaspore,  p  349,  AIO(OH) 
H=6.5.    Pearly,  pink  to  brown. 
0.  Andalusite,  P.  404,  Al(AlO)SiO4 
H=7to7.5.    Square  nrisms. 
H.  Phenacite,  p.  399,  Be,,SiO4 
H=7.5to8.    Resembles  quartz. 
I.  Spinel,  p.  341,  MgAl204 
H=8.    Octahedrons. 
O.  Topaz,  p.  403,  A1(A1(OF,)S1O4 
H=8.     Prisms  with  basal  cleavage. 
0.  Chrygoberyl,  P-  353,  BeAl,o4 
H=8.o.    Tabular,  yellow  or  green. 
H.  Corundum,  p.  346,  Al2o3 
H=8-9.    G=4.    Adamantine. 

T.  Octahedrite,  p.  252,  TiOa 
Brown  or  blue  pyramids.  Adaman- 
tine. 
T.  Rutlle.  p.  251,  TiOa 
Red  to  black.    Adamantine  pris- 
matic, often  needles.    G=4.2. 
T.  Cassiterite.  p.  249,  SnO, 
Brownish-black.  Adamantine, 
G=6.8  to  7.1. 
H.  Quartz,  p.  372,  SiO, 
H=7.    G=2.65. 
H.  Tridymite,  p.  376,  SIO, 
Minute  tabular  crystals. 
-.  Opal,  p.  376,  Si()2nHaO 
H=5.5to6.5.    G=2.1to2.2.    Frac- 
ture conchoidal. 
T.  Zircon,  p.  402,  ZrSlO4 
H=7.5.    Pyramid  and  prism. 

Fe(AlO)4(Al6H)(Si04) 
H=7.5.    Prisms.   Usually  twinned. 
H.  Tourmaline,  R,8B2(8io«)4 
H=7.5.    Hemimorphic.     P.  409. 
I.  Garnet,  p.  396,  Uvarovite, 
Ca,Cra(SiO4)3 
H=7.5.    Emerald  green  crystal*. 
I.  Diamond,  p.  366,  c 
H-ia    Adamantine.    G=8.61. 

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Aluminium Al 

Antimony Sb 

Argon A 


INTERNATIONAL   ATOMIC   WEIGHTS. 
0  =  16.  H  =  l. 

27.1        26.9          Neodymium.    .  .  Ne 

I2O.2       II9.3 

39-9       39-6 


Arsenic As 

Barium Ba 

Beryllium  (Glucinum)  .  Be 

Bismuth Bi 

Boron B 

Bromine Br 

Cadmium Cd 

Caesium Cs 

Calcium Ca 

Carbon    ....'...  C 

Cerium Ce 

Chlorine Cl 

Chromium Cr 

Cobalt Co 

Columbium  (Niobium).  Cb 

Copper Cu 

Erbium .    .  E 

Fluorine F 

Gadolinium Gd 

Gallium Ga 

Germanium Ge 

Gold Au 

Helium He 

Hydrogen H 

Indium In 

Iodine I 

Iridium Ir 

Iron Fe 

Krypton Kr 

Lanthanum La 

Lead Pb 

Lithium Li 

Magnesium Mg 

Manganese Mn 

Mercury Hg 

Molybdenum Mo 


7S-o 

137-4 

9-i 

208.5 

ii 


74-4 

136.4 
9-03 

206.9 
10.9 
79-36 

in. 6 

132 
39-8 
11.91 

139 
35-18 
51-7 
58.56 
93-3 
63-1 

164.8 
18.9 

155 
69.5 
71.9 

195-7 

4 

1.008     i.ooo 
114        113.1 
126.85   125.90 
193.0     191.5 

55-9      55-5 
81.8      81.2 
138-9     137-9 
206.9     205.35 
7.03      6.98 
24.36    24.18 
55-o      54-6 
200.  o     198.5 
96.0      95.3 
427 


112.4 

133 
40.1 

12. OO 
I40 

35-45 
52.1 
59-0 
94 
63.6 
1 66 

'9 
,56 
70 

72-5 
197.2 

4 


Neodymium.  . 
Neon  .... 

Nickel    .    .  . 

Nitrogen     .  . 

Osmium .    .  . 

Oxygen  .    .  . 

Palladium  .  . 

Phosphorus  . 

Platinum    .  . 

Potassium  .  . 
Praseodymium 

Radium  .    .  . 

Rhodium    .  . 

Rubidium  .  . 

Ruthenium.  . 

Samarium  .  . 

Scandium.  .  . 

Selenium.    .  . 

Silicon    .    .  . 

Silver.    .    .  . 

Sodium  .    .  . 

Strontium   .  . 

Sulphur  .    .  . 

Tantalum    .  . 

Tellurium  .  . 

Terbium .    .  . 

Thallium    .  . 

Thorium.    .  . 
Thulium.    . 


Titanium. 
Tungsten 
Uranium. 
Vanadium 
Xenon  . 
Ytterbium 
Yttrium  . 
Zinc  .  . 
Zirconium 


.  Ni 
.  N 
.  Os 
.0 
.  Pd 
.  P 
.  Pt 
.  K 
.Pr 
.  Ra 
.  Rh 
.  Rb 
.  Ru 
.  Sm 
.  Sc 
.  Se 
.  Si 
-  Ag 
.  Na 
.  Sr 
.  S 
.  Ta 
.  Te 
.  Tb 
.  Tl 
.  Th 
.  Tm 
.  Sn 
.  Ti 
.  W 

.u 
.  v 

.  X 

.  Yb 

,  Yt 

.  Zn 

Zr 


0  =  16. 

143-6 

20 
58.7 
14.04 
I9I 

16.00 
106.5 

31.0 
194.8 

39-15 

140.5 

225 

103.0 
85.4 

101.7 

150 
44.1 
79-2 
28.4 

107-93 
23-05 
87.6 
32.06 

183 

127.6 

160 

204.1 

232.5 
171 
119.0 
48.! 
184.0 

238.5 
51.2 

128 

173-0 
89.0 
65-4 
90.6 


142.5 
19-9 
58-3 
'3-93 

189.6 
15-88 

105.7 
30.77 

'93-3 
38.86 

'39-4 

223-3 

IO2.2 
84.8 
IOO.9 
148.9 

43-8 

78.6 

28.2 

107.12 

22.88 

86.94 
31-83 
181.6 
126.6 

158.8 
202. 6 
230.8 
169.7 

i  is.  i 

47-7 
182.6 
236.7 
50.8 
127 
171.7 
88.3 
64.9 
89-9 


GENERAL   INDEX. 


Abrasives,  250,  345,  371,  372 
Absorption  in  doubly  refracting  crystals,  1 75 

in  isotropic  crystals,  175 
Accessory  minerals,  195 
Acicular  habit,  130 
Acid,  potassium    sulphate,  reactions  with, 

100 

Acids,  uses  of  in  blowpipe  work,  99 
Actinium,  effect  on  phosphorescence,  156, 

245 

Acute  bisectrix,  171 
Adamantine  lustre,  154 
Aggregates,  crystal,  137 

external  form,  141 

internal  structure,  137 
Alteration,  192 
Aluminates,  187 
Alum,  source  of,  349,  352 
Aluminum,  summary  of  tests,  102 

see  also,  91,  100,  122,  126 

supports,  78 
Aluminum  minerals,  343 

uses  and  extraction,  343 
Ammonium,  summary  of  tests,  102 
Ammonium  minerals,  317 
Amorphous  condition,  130 
Amygdaloidal,  142 
Analysis,  Blowpipe,  82,  101 
Angle  between  optic  axes,  173 

of  least  deviation,  158 
Angles  of  crystals,  3,  4,  7 
Angles  changed  by  expansion,  177 
Antimonides,  189 
Antimony,  summary  of  tests,  IO2 

see  also,   89,   90,   94,   99,    117,    118, 

119,     120 

Antimony  minerals,  272 

uses  and  extraction,  272 
Anvil,  78 
Apparatus,  75 
Arborescent,  142 
Arsenates,  187 
Arsenic,  summary  of  tests,  103 

4 


Arsenic,  sources,  208,   215 

uses  and  extraction,  270 

metallic,  270 

white,  270 

see  also,  89,  90,  91,  94,  99,  117,  125 
Arsenic  minerals,  270 
Arsenides,  186 
Asphalt,  364 
Associates,  191 
Asterism,  155 

Atomic  weights,  table  of,  427 
Axes,  crystallographic,  17,  20 

choosing,  2O,  23,  26,  31,  37,   43,    46, 

49,  52,  56,  59 

interchangeable,  20 

of  symmetry,  10,  II,  16 

of  the  six  systems,  2 1 

optic,  167 
Axial  angle,  measurement,  173 

changed  by  heat,  177 
Axial  cross,  construction,  67 

elements,  graphic  determination,  71 

Balance,  Jolly's,  149 
Barium  salts,  320 

see  also,  91,  122,  125,  127 

summary  of  tests,  104 
Barium  minerals,  319 

uses  and  production  of,  319 
Basal  pinacoid,  24,  28,  33,  38,  43,  50 

plane,  47 

Basic  silicates,  409 
Beads,  how  to  make,  80 
Bead  tests,  95 

table  of,  97 
Bell  metal,  248,  282 
Berzelius  lamp,  77 

Biaxial    crystals    in    convergent    polarized 
light,  171 

in  parallel  polarized  light,    167 
Bisectrix,  acute  and  obtuse,  171 
Bismuth,  summary  of  tests,  104 

see  also,  89,  90,  91,  94,  98,  119,   120 
8 


GENERAL    IXDEX. 


429 


Bismuth  minerals,  266 

uses  and  extraction,  267 
Bismuth-flux,  composition,  90 

reactions  with,  90 
Bitumens,  364 
Bladed  structure,  139 
Blast,  method  of  blowing,  79 
Blowpipe  analysis,  scheme  for,  1 1 7 

operations  of,  82,  IOI 
Blowpipe  apparatus,  75 
Blowpipe,  description  of,  75 
Blowpipe  lamps,  76 
Blowpipe  tests,  summary  of,  IO2 
Bluestone,  370 
Borates,  187 
Borax,  production  of,  355 

reactions  with,  95,  97 

how  to  make  bead,  80 
Borax  lakes,  minerals  of,  204 
Boric  acid  flux,  reactions  with,  IOI 
Boric  acid,  uses,  101 

production  of,  355 
Boron,  summary  of  tests,  104 

see  also,  124,  125 
Boron  minerals  and  their  uses,  355 
Botryoidal,  141 
Brachy  dome,  33 

pinacoid,  24,  33 

pyramid,  32 
Brass,  241,  282 
Braun's  solution,  151 
Brittle,  146 
Bromides,  186 
Bromine,  summary  of  tests,  104 

see  also,  93,  100,  123,  312 
Bronze,  248,  282 
Bronze  aluminum,  345 
Building  stones,  369 
Bunsen  burner,  76 

Cadmium  borotungstate  solution,  151 

mineral,  246 

source,  243,  247 

summary  of  tests,  105 

see  also,  91,  94,  98,  118 

use  and  extraction,  247 
Caesium,  tests  for,  87 
Calcium  minerals,  uses  and  production, 

see  also,  87,  91,  122,  125,  127 

summary  of  tests,  105 


Capillary  habit,  130 

Carbonated  water,  solvent  power,  198 

Carbonates,  181,  186,  200 

from  spring  waters,  200 
Carbon  minerals  and  their  uses,  362-366 
Carbon  dioxide,  summary  of  tests,  105 

source  of,  341 

see  also,  93,  108,  124,  125 
Cements,  see  hydraulic  cements,  324 
Characters  of  minerals,  128,  et  seq. 
Charcoal,  method  of  using,  87 

forms  used,  77 

reactions  obtained  on,  89 
Chart,  spectroscopic,  86 
Chemical  balance  for  sp.  gr.,  149 

composition  and  reactions,  181,  199 

salts,  128 
Chlorides,  186 
Chlorine,  summary  of  tests,  105 

see  also,  100,  105,  123 
Chromates,  186 
Chromium,  from  chromite,  208,  225 

see  also  94,  97,  121 

summary  of  tests,  105 
Clay,  371 
Cleavage,  143 

terms  of,  144 

method  of  obtaining,  144 
Clino  dome,  27 

pinacoid,  28 

Closed  tubes,  reactions  in,  93 
Coal,  366 

Cockscomb,  forms,  136 
Cobalt,  extraction  of,  233 

see  also,  91,  97,  98,  99,  101,  118,  122 

solution,  reactions  with,  100 

summary  of  tests,  106 
Cobalt  minerals,  233 

uses  and  production,  233 
Cohesion,  characters  dependent  on,  143 
Color,  causes  of,  155 

changes  in  closed  tubes,  94 

(reduction)  tests,  98 

rings,  172 

terms  used,  155 
Coloration  of  flame,  83 
Colors,  interference,  165 
303    Columbates,  188 

Columbium  salts,  225 
Columnar  structure,  137 


430 


GENERAL    lA'DEX. 


Composition  of  minerals,  184 
Conchoidal,  146 
Conductivity  of  heat,  177 

electrical,  179 
Contact  goniometers,  4 
Contact  minerals,  196 
Convergent  polarized  light,  1 68 
Copper,  summary  of  tests,  106 

see  also,  91,  94,  97,  98,  101,  119,  122 
Copper  minerals,  279 

uses,  production  and  extraction,  279 
Copper  sulphate,  282 
Copperas,  212 
Coraloidal,    142 
Corroded  faces,  132 
Crossed  nicols,  161 
Crystal  drawing,  67 

systems,  20 
Crystalline  aggregates,  137 

condition,   129 

structure,  explanation  of,  I 
Crystallization,  I 
Crystallographic  axes,  17,  20 
Crystals,  aggregates,  137 

angles  of,  3 

classification,  6 

curved  faces,  131 

definition,  I 

forms,   1 8 

habit,  130 

inclusions,  132 

irregularities  of  faces,  130 

law  of  constancy  of  angles,  3 

measurement  of,  4,  7 

parallel  growth,  134 

positive  and  negative,  70*  I72 

regular  grouping,  133 

striations,  130 

symmetry  of,  10 

twinning,  6 1 
Cube,  54 
Cupel  holder,  78 
Curved  faces  of  crystals,  131 

Deltohedron,   57 
Dendritic,  142 
Depolarization,  162 
Destructive  interference,  163 
Diamagnetism,  178 
Dichroscope,  176 


Dihexagonal  pyramid,  49 

prism,  44 
Diploid,  59 
Ditetragonal  prism,  32,  38 

pyramid,  37 
Ditrigonal  prism,  47 
Dodecahedron,  54 
Domes,  24,  27,  33 
Double  refraction,  159 

strength  of,  165 
Drawing  crystals,  67 
Drusy  faces,  131 
Ductile,  146 
Dull  in  lustre,  154 

Elasticity,  145 

Elastic,  145 

Electrical  characters,  178 

conductivity,  179 
Elements,  185 

isomorphous,  182 
Epigenesis,  192 
Epsom  salts,  source,  339 
Etching  figures,  147 
Etched  crystals,  132 
Evaporation,  199 
Exhalations,  minerals  due  to,  197 
Expansion  of  crystals  by  heat,  177 

change  of  angle  by,  177 

change  of  optical  characters  by,  178 
External  form  aggregates,  141 
Extinction  between  crossed  nicols,  161 
Extinction  directions,  163 

Feel,  terms  used,  153 

Ferro-manganese,  227 

Fertilizers,  310 

Fibrous  structure,  139 

Fireworks,  materials  used  in,  271,  272 

Flame  colorations,  83 

oxidizing,  79 

reducing,  80 

structure  of,  79 
Flaming,  98 
Fletcher  lamp,  77 
Flexible,  145 
Fluorescence,  156 
Fluorides,  186 
Fluorine,  summary  of  tests,  107 

see  also,  93,  100,  124 


GENERAL    I. \D1-.X. 


431 


Flux,  326,  336,  356 

Foliated  structure,  139 

Forceps,  78 

Form,  ideal,  1 1 

Forms,  definition,  1 8 

Formulae  of  minerals,  determining,  184,  188 

Fracture,  146 

Frictional  electricity,  179 

Fuess  goniometer,  8 

Fuess  microscope,  162 

Fuess  universal  apparatus,  174 

Fusibility,  scale  of,  82 

how  to  test,  82 
Fusion,  manner  of,  83 
Fusion-solutions,   194 

Gas  blowpipe,  76 

Gems,  345,  366,  372,  377 

General  characters,  148 

Genesis,  of  minerals,  191-205 

Geode,  136 

German  silver,  282 

Glass,  materials  used  in,    227,  270,  275, 

277,  313,  371 
Glide  planes,  145 
Gold  from  iron  minerals,  208,  215 

from  copper  ores,  282 

from  silver  ores,  295 

tests  for,  91,  99,  119,  123 

uses  of  with  beads,  98 
Gold  minerals,  303 

uses,  production  and  extraction,  303 
Goniometers,  contact,  4 

Fuess',  8 

two  circle  contact,  5 

Miller's  substitute,  7 
Granular  structure,  139 
Granite,  370 

Graphic  solution  of  stereographic  projec- 
tions, 71 

Greasy  lustre,  154 

Ground  water,  minerals  formed  by,  201 
Gunpowder,  310 
Gypsum  test  plate,  167 

Habits  of  crystals,  130 
Hammer,  78 
Hand-goniometers,  4 
Hardness,  146 
scale  of,  147 


ieat,  conductivity,  177 

expansion,  177 
ieat  rays,  transmission,  177 

specific,  152 
ieating  power  of  flame,  82 
ieavy  liquids,  use  of,  150 

i  prism,  24 

pyramid,  27 

brachy  dome,  24 

macro  dome,  24 

ortho  dome,  27 
:Iemimorphic  ditrigonal  pyramid,  47 

hexagonal  pyramid,  second  order,  47 

triagonal  pyramid,  first  order,  47 
rlexagonal  axial  cross,  68 
rlexagonal  crystals,  in  convergent  polarized 
light,  169 

in  parallel  polarized  light,  167 
Hexagonal  prism  of  first  order,  44 

prism  of  second  order,  44 

pyramid  of  first  order,  50 

pyramid  of  second  order,  43 
Hexagonal   system,   dihexagonal   pyramid 
class,  49 

combinations,  50 

type  forms,  49 
Hexagonal  system,  hemimorphic  class,  46 

combinations,  48 

type  forms,  47 
Hexagonal  system,  other  classes  in,  48,  51 
Hexagonal  system,  scalenohedral  class,  42 

combinations,  44 

symmetry,  42 

type  forms,  43 
Hexagonal  twins,  65 
Hexahedron,  54 
Hextetrahedron,  57 
Hexoctahedron,  52 
Hollow  crystals,  132 
Homogeneity,  183 
Hydrofluoric  acid,  source,  326 
Hydrogen  minerals,  3O1 
Hydrous  silicates,  412 
Hydraulic  cements,  324 
Hydroxides,  185 

Iceland  spar,  uses,  336 
Ideal  forms,  1 1 
Impalpable  structure,  141 
Inclusion s  in  crystals,  132 


432 


GENERAL   INDEX. 


Incandescent  mantles,  254 
Index  of  refraction,  157 

measurements  of,  157,  158 
Indices  of  Miller,  2O 

graphic  determination,  71 
Indium,  tests  for,  87 
Interchangeable  axes,  20 
Interference  between  crossed  nicols,  163 
Interference  colors  with  white  light,  165 
Interference,  destructive,  163 
Interference  figure,    168,  172 
Intercepts,  17 

law  of  rational,  18 
Internal  structure  aggregates,  137 
Iodides,  186 
Iodine,  summary  of  tests,  107 

see  also  93,  100,  123 

source,  312 

Iridescence,  definition,  155 
Iridium  minerals,  308 
Iridium,  uses  and  extraction,  308 
Iron,  summary  of  tests,  108 

see  also  91,   94,   97,    99,    101,    118, 
1 20,  122 

source  of,  206 
Iron  minerals,  206 

method  of  extraction,  207 

uses  and  production  of,  206-208 
Irregularities  of  crystals,  130 
Isometric  crystals,  drawing  axial  cross,  67 

in  convergent  polarized  light,  169 

in  parallel  polarized  light,  167 
Isometric  system,  diploid  class,  59 

combinations,  60 

type  forms,  59 
Isometric  system,  hexoctahedral  class,  52 

combinations,  54 

symmetry,  52 

type  forms,  52 
Isometric  system,  hextetrahedral  class,  56 

combinations,  57 

type  forms,  56 

Isometric  system,  other  classes  in,  60 
Isometric  twins,  66 
Isomorphic  elements,  182 

mixtures,  183 
Isomorphism,  181 

Jolly's  balance,  use  of,  149 


Klein's  solution,  151 

v.  Kobell's  scale  of  fusibility,  82 

Lakes,  minerals  formed  in,  202 
Lamellar  structure,  139 
Lamps,  blowpipe,  76 

oils  used  in,  77 
Law  of  constancy  of  interfacial  angles,  3 

of  rational  intercepts,  18 

of  symmetry,  16 
Lead,  method  of  extraction,  255 

summary  of  tests,  108 

see  also  89,  90,  91,  94,  99,  101,  119 
1 20 

uses  of  with  beads,  98 
Lead  minerals,  255 

uses,  production  and  extraction,  255 
Lime,  production,  324 
Limestone,  production  and  uses,  324 
Lithium,  summary  of  tests,  109 

see  also,  87,  101,  125 

salts,  source,  315 

Lithium  minerals,  uses  and  production,  31  = 
Lithographic  stone,  336 
Lustre,  154 

Macles,  61 
Macro  dome,  33 

pinacoid,  24,  33 

pyramid,  33 
Magma,  195 
Magnesium,  summary  of  tests,  109 

extraction,  339 

see  also,  71,  100,  122,  126 
Magnesium  minerals,  and  their  uses,  339 
Magnesium  ribbon,  tests  with,  loo 
Magnetic  characters,  178 
Magnetism,  178 
Malleable,  146 
Manganese,  summary  of  tests,  109 

see  also,  97,  99,  101,  121 
Manganese  minerals,  227 

uses  and  production  of,  227 
Marble,  production,  324 
Mass  action,  199 
Matches,  materials  used  in,  274 
Measurement  of  interfacial  angles,  4,  7 
Mercury  minerals,  293 

uses,  production  and  extraction,  293 


GENERAL   1XD1-.X. 


433 


Mercury,  summary  of  tests,  I IO 

see  also,  90,  94,  99,  120,  125 
Melallic  lustre,  154 
Metasilicates,  383 
Methylene  iodide,  151 
Micaceous  structure,  139 
Mica  test  plate,  166 
Microscope,  polarizing,  162,  168 
Miller's  indices,  20 
Mineralogy,  definition,   129 
Minerals,  definition,  128 
Minerals,  iron,  etc.,  see  Iron  minerals,  etc. 
Mixed  crystals,  182 
Moh's  scale  of  hardness,  147 
Molybdates,  187 
Molybdenum  summary  of  tests,  1 10 

see  also,  80,  89,  90,  91,  92,  99,  121, 

"5 
Molybdenum  minerals,  277 

uses,  277 

Molybdenum  salts,  278 
Molybdic  acid,  277 
Monochromatic  light,  interference  with,  163 

index  of  refraction  with,  157 
Monoclinic  crystals  in  convergent  polarized 
light,  171,  174 

in  parallel  polarized  light,  167 

drawing  axial  cross,  68 
Monoclinic  system,  other  classes  in,  29 
Monoclinic  system,  prismatic  class,  26 

axes  of,  26 

combinations,  28 

type  forms,  26 
Monoclinic  twins,  63 
Mossy  forms,  142 

Natural  gas,  363 

Negative  crystals,  uniaxial,  170 

biaxial,  172 
Nickel,  extraction  of,  237 

from  iron  minerals,  208 

summary  of  tests,  1 1 1 

see  also,  91,  97,  98,  99,  101,  118,  121 
Nickel  minerals,  236 

uses  and  production  of,  236 
Nicol's  prism,  161 
Nitrates,  186 
Nitric  acid,  summary  of  tests,  1 1 1 

see  also,  123 
Nodular,  141 
28 


Non-metallic  lustre,  154 
Norremberg's  polariscope,  169 

Obtuse  bisectrix,  171 

Oceans,  minerals  formed  in,  202 

Occurrence  of  minerals,  191 

Ochre,  206 

Octahedron,  53 

Odors  in  closed  tubes,  93 

in  open  tubes,  95 

terms  used,  152 
Oil  and  oil -lamps,  77 
Oolitic,  141 
Opalescence,  155 
Opaque,  157 

Open  tubes,  reactions  in,  94 
!  Optic  axes,  determination  of  angle,  173 
Optic  axis,  uniaxial,  167 

biaxial,  167 
Optical  characters,  154,  et  seq. 

changed  by  expansion,  178 
distinctions  between  systems,  167 
Organic  substances,  128 
Organisms,  minerals  formed  by,  204 
Origin  of  minerals,  191 
Ortho  pinacoid,  28 

in   convergent   polarized    light,    171, 

174 

Orthorhombic  crystals  in  parallel  polarized 
light,  167 

drawing  axial  cross,  67 
Orthorhombic  system,  30 

axes  in,  31 

series,  30 

symbols  for  individual  faces,  30 
Orthorhombic  system,  other  classes,  35 
Orthorhombic  system,  pyramidal  class,  31 

combinations,  34 

type  forms,  31 
Orthorhombic  twins,  64 
Orthosilicates,  394 
Oxidation  by  means  of  blowpipe,  79 
Oxides,  185 
Oxidizing  flame,  79 

Paints,  natural,   206,  219,  222,  271,  272, 

275,  291,  294,  368,  418 
Paragenesis,  191 
Paramagnetism,  178 
Parallel  growth  of  crystals,  134 


434 


GENERAL   INDEX. 


Parallel  polarized  light,  162 

distinguishing  system  by,  167 
Paris  green,  270 
Parting,  143 
Pearly  lustre,  154 
Penfield's  goniometer,  4 

protractor,  15 

solution,  152 
Percussion  figures,  145 
Petroleum,  363 
Pewter,  248 
Phantom  effects,  135 
Phosphate  rock,  production,  325 
Phosphates,  187 
Phosphorescence,  155 
Phosphorus,  source  of,  331 

summary  of  tests,  III 

see  also,  98,  124 
Piezoelectricity,  180 
Pigments,  see  paints 
Pinacoid,  see  basal,  brachy,  clino,  macro, 

and  orthopinacoids 
Pisolitic,  141 
Plane,  basal,  47 

of  polarization,  160 

of  symmetry,  10,   n,  16 

of  vibration,  159 
Plaster  of  Paris,  production,  324 
Plaster  tablets,  use,  88 

preparation,  77 

sublimates  on,  89 
Platinum  minerals,  308 

production,  308 
Platinum  wire  and  holder,  78 
Play  of  color,  155 
Pleochroism,  175 
Pliable,  145 
Plumose,  142 
Plutonic  rocks,  196 
Polariscope,  for  parallel  light,  162 

for  convergent  light,  1 68,  169 
Polarized  light,  161 
Polarizing  microscope,  162 
Polysilicates,  377 
Polysynthetic  twins,  62 
Porcelain,    materials   used   in,    251,    275, 

277,  371,  372 
Positive  crystals,  uniaxial,  170 

biaxial,  172 
Potassium,  summary  of  tests,  1 1 1 


|  Potassium,  see  also,  87,  125,  127 

Potassium  bisulphate,  reactions  with,  100 
bromide,  310 

chlorate,  reactions  with,  101 
nitrate,  309 

Potassium  minerals,  309 

uses  and  production,  309 

Pottery,  materials  used  in,  277,  313,  372 

Precipitation  from  watery  solutions,  199 

Primary  minerals,  194 

Pressure,  effect  on  solvent  power,  199 

Principal  vibration  directions,  171 

Prism,  see  brachy,  clino,  dihexagonal, 
ditetragonal,  ditrigonal,  hemi,  hexagonal, 
macro,  ortho,  rhombic,  tetragonal,  tri- 
gonal 

Prism  method  for  Indices  Refraction,  158 

Prismatic  habit,  130 

Projection  stereographic,  13 

Protractor,  Penfield's,  15 

Pseudomorphs,  192 

Pseudo  symmetry,  62 

Pycnometer,  150 

Pyramid,  see  clino,  dihexagonal,  ditetra- 
gonal, hemi,  hemimorphic,  hexagonal, 
orthorhombic,  tetragonal,  trigona' 

Pyramidal  habit,  130 

Pyritohedron,  60 

Pyroelectricity,  179 

Qualitative  blowpipe  analysis,  117 
Quarter  undulation  mica  plate,  1 66 
Quartz  wedge,  165 

scepter,  134 

capped,  135 

Radiating  crystals,  135 
Radium,  source,  275,  277 

effect  on  phosphorescence,  156, 245, 3 1  ^ 

effect  on  fluorescence,  156 
Rain,  198 

Rational  interceps,  18 
Reagent  bottles,  78 
Reducing  flame,  80 
Reduction  by  flame,  80 

by  tin,  98 

with  metallic  sodium,  92 

with  soda,  91 
Reduction  color  tests,  98 
Reflection,  total,  158 


GENERAL   INDEX. 


435 


Reflection,  twins,  61 

goniometers,  7,  8 
Refraction,  definition,  157 

double,  159 

index  of,  157 

Regular  grouping  of  crystals,  133 
Reniform,  141 
Repetition,  192 
Resinous  lustre,  154 
Resins,  365 
Reticulated,  136 
Rhombic  prism,  33 

pyramid,  32 

Rhombohedron  of  the  first  order,  43 
Rock,  definition,  128 

volcanic,  195 

plutonic,  196 
Rosette,  136 

Rotation,  direction  of,  170 
Rotation  twins,  61 

Rubber,  materials  used  in,  272,  274,  361 
Rubidium,  tests  for,  87 

Salt  deposit,  Stassfurt,  202 

Salt,  production,  312 

Salt  of  phosphorus,  reactions  with,  95,  97 

bead,  how  to  make,  80 
Salts,  chemical,  128 
Sandstone,  370 
Scale  of  hardness,  Moh's,  147 

fusibility,  v.  Kobell's,  82 
Scalenohedron,  hexagonal,  43 
Schemes  for  blowpipe  analysis,  117 

for  determination  of  minerals,  after  426 
Seas,  minerals  formed  in,  202 
Sectile,  146 
Selenides,  189 
Selenium,  summary  of  tests,  1 12 

see  also,  89,  90,  91,  94,  119 
Separation  from  magma,  195 

from  watery  solutions,  197,  199 

from  fusion  solutions,  195 
Series,  30,  36 
Sheaf  like,  142 
Shot  metal,  270 
Sienna,  206 
Silica,  222 

from  spring  water,  200 
Silicates,  and  their  uses,  369 
Silicates,  188 


Silicate  magma,  195 

Silicon,  summary  of  tests,  112 

see  also,  91,  122,  125 
Silky  lustre,  154 
Silver,  summary  of  tests,  112 

in  manganese  ores,  227 

in  lead  ores,  255,  258,  263 

in  copper  ores,  282,  288 

see  also,  91,  99,  119,  123 
Silver  minerals,  295 

uses,  production  and  extraction,  295 
Simple  mathematical  ratio,  law  of,  18 
Slate,  370 
Smalt,  233 

Soda,  reactions  with,  90 
Soda  lakes,  minerals  of,  203 
Sodium  carbonate,  90,  312 
Sodium,  reactions  with,  92 

precautions  with,  92 

summary  of  tests,  1 13 

see  also,  87,  125 
Sodium  minerals,  311 

production  and  uses,  312 
Sodium  thiosulphate,  reactions  with,  99 

uranate,  275 
Solder,  248 

Solidification  of  chemical  substances,  184 
Solid  solutions,  182 
Solids  in  ocean  and  rivers,  202 
Solubility  tests,  99 
Solvent  power  of  water,  198 
Solutions,  fusion,  194 

solid,  182 

watery,  197,  199 
Species,  mineral,  129 
Specific  gravity  determination,  148 

flask,  150 
Specific  heat,  152 
Spectroscope,  use  of,  84 

chart,  86 

Spiegeleisen,  217,  224,  230 
Springs,  minerals  from.  199 
Stalactitic,  141 
Stassfurt  salt  deposit,  202 
Stereotype  metal,  272 
Steel,  production,  207 

materials  used  in,  208,  227,  236,  275, 

277,  279.  339 

Stereographic  projection,  13 
graphic  determination,  71 


436 


GENERAL    IXDEX. 


Streak,  definition  and  determination,  156 
Striations  of  crystals,  130 
Structure  of  aggregates,  137 

of  crystals,  I 
Strontium,  summary  of  tests,  113 

salts,  321 

see  also,  91,  122,  125,  127 
Strontium  minerals  and  their  uses,  321 
Structure,  crystal,  I,  2 
Sublimates  in  closed  tubes,  94 

in  open  tubes,  95 

on  charcoal,  89 

on  plaster,  89 
Subsilicates,  409 
Succession,  192 
Sulphates,  1 86 
Sulpharsenites,  187 
Sulphantimonides,  187 
Sulphides,  186 
Sulphur  deposits,  197,  2OO 
Sulphur  extraction,  359 

from  pyrite,  208 

summary  of  tests,  1 13 

see  also,  94,  119 
Sulphur  minerals  and  their  uses,  359 

from  spring  water  200 
Sulphuric  acid,  212,  359 
Summary  of  blowpipe  tests,  IO2 
Supports  for  blowpiping,  77 
Surface  conductivity,  180 
Symbols  of  Weiss,  19 

of  Miller,  20 

for  individual  faces,  30 
Symmetry  of  crystals,  Id 

axes  of,  10,  n,  16 

determination,  II,  12,  16 

geometric,  1 1 

planes  of,  10,  II,  16 

law  of,  1 6 

Synthesis  of  mineral,  193 
Systems,  the  six  crystal,  2O 
System,  determination,  by  polarized  light, 
167 

by  symmetry,   16 

Tables  for  mineral  determination,  after  426 
Tabular  habit,  130 
Tantalates,  1 88 
Tantalum  salts,  225 
Tarnish,  definition,  155 


Taste,  terms  used,  152 

Tellurides,  186 

Tellurium,  summary  of  tests,  113 

see  also,  90,  91,  94,  119 
Tellurium  minerals,  359 
Tenacity,  146 
Tetragonal  crystals,  drawing  axial  cross,  67 

in  convergent  polarized  light,  169 

in  parallel  polarized  light,  167 
Tetragonal  prisms  of  first  order,  39 

prisms  of  second  order,  38 

pyramid  of  first  order,  37 

pyramid  of  second  order,  37 
Tetragonal   system,    ditetragonal   pyramid 
class,  36 

series  and  combinations,  36,  39 

symmetry  of,  36 

type  forms,  37 

Tetragonal  system,  other  classes,  41 
Tetragonal  twins,  64 
Tetrahedron,  57 
Tetrahexahedron,  53 
Tetrapyramid,  23 
Thallium,  tests  for,  87 
Thermal  characters,  177 
Thermit,  345 
Thermo-electricity,  179 
Thorium  minerals,  252 

extraction,  253 

uses  and  production  of,  253 
Thoulet  solution,  151 
Tin,  summary  of  tests,  114 

see  also,  89,  90,  91,  94,  99,  loo,  118, 
119,  122 

uses  with  fluxes,  98 

uses  in  color  tests,  98 
Tin  amalgam,  248 
Tin  minerals,  248 

extraction,  248 

uses  and  production,  248 
Tin  plate,  248 
Titanium,  summary  of  tests,  1 14 

see  also,  97,  99,  100,  120,  122,  126 
Titanium  minerals,  250 

uses  and  production,  25 1 
Titano-silicates,  424 
Total  reflection,  158 
Tough,  146 
Translucency,  157 
Transparent,  157 


GENERAL    IXIU-.X. 


437 


Trapezohedron,  53 

Triclinic  crystals  in  parallel  polarized  light, 
167 

in  convergent  polarized  light,  171,  175 

drawing  axial  cross,  68 
Triclinic  system,  pinacoidal  class,  23 

axes,  23 

type  forms,  23 

combinations,  24 
Triclinic  system,  other  classes,  25 
Triclinic  twins,  63 
Trigonal  prism,  first  order,  47 
Trisoctahedron,  53 
Tristetrahedron,  57 
Tube  tests,  93,  94 
Tungstates,  187 
Tungsten,  summary  of  tests,  114 

see  also,  91,  97,  99,  120 

extraction  and  uses,  208,  226,  339 
Twin  crystals,  61 

axis,  62 

hexagonal,  65 

isometric,  66 

monoclinic,  63 

orthorhombic,  64 

plane,  61 

tetragonal,  64 

triclinic,  63 
Twinning,  secondary,  63 

polysynthetic,  131 
Type  symbols,  21 
Type  metal,  272 
Types  of  mineral  compounds,  185 

Ultra-violet  light,  effects,  156,  245,  317 
Umber,  206,  222 

Uniaxial  crystals,  in  convergent  polarized 
light,  169 

in  parallel  polarized  light,  167 
Unit  prism,  33 

pyramid,  32 
Uranium,  summary  of  tests,  115 

salts,  275 

see  also,  97,  99,  12 1 

yellow,  275 


Uranium  minerals,  275 

uses  and  production,  275 

Vanadinates,  188 
Vanadium,  265 

black,  265 

salts,  265 

see  also,  91,  97,  99,  121 

summary  of  tests,  115 
Vanadium  minerals,  264 
Veins,  minerals  deposited  in,  201 
Vermilion,  293 
Vibration  directions  of  faster   and  slower 

rays,  1 66 

Vibration  directions,  163 
Vibrations,  planes  of,  159 
Vicinal  faces,  132 
Vitreous  lustre,  154 
Volatilization,  elements  affected,  87 
Volcanic  rocks,  195 

Water,  mineral,  consumption,  361 
Water,  tests  for,  93,  125 
Water  solvent  power,  198 
Watery  solutions,  minerals  from,  197 

solids  from,  199 
Waxes,  mineral,  365 
Wedge  for  interference  colors,  164,  165 
Weiss' s  symbols,  19 
Westphal's  balance,  use  of,  150 
White  lead,  255,  263 

adulterants  of,  319,  321 
Wire  like,  142 

X-Rays,  effects  on  phosphorescence,   156, 
245.  3!7 

Zeolites,  412 

Zinc,  extraction  of,  241 

summary  of  tests,  1 1 5 

see  also,  89,  91,  94,  99,  100,  118 
Zinc  minerals,  241 

uses  and  production  of,  241 
Zinc  white,  production  of,  217,  241 
Zone  relations,  71 


INDEX   TO   MINERALS 


Names  of  described  species  are  in  heavier  type,  varieties  and  synonyms  in  lighter  type  ; 
the  first  numbers  refer  to  the  descriptions. 


Acmite,  386 
/Eschynite,  252 
Actinolite,  390 
Adamantine  spar,  347 
Adularia,  380 
Agate,  372,  375 
Agolite,  421 
Aikinite,  268 
Alabandite,  228 
Alabaster,  328,  329 
Albertite,  364 
Albite,  382,  62 
Alexandrite,  354 
Allanite,  408 
Almandite,  397 
Aluminite,  351 
Alum  stone,  351 
Alunite,  351 
Alunogen,  351 
Amalgam,  298 
Amazonstone,  381 
Amber,  365 
Amber  mica,  419 
Amblygonite,  316 
Amethyst,  374 
Amphibole,  389,  28 
Analcite,  415 
Andalusite,  404 
Andesite,  383 
Andradite,  397 
Anglesite,  259 
Anhydrite,  327 
Ankerite,  337 
Annabergite,  239 
Anorthite,  382 
Anorthoclase,  381 
Antimony,  273 
Apatite,  330 
Aphthitalite,  311 
Apophyllite,  413,  40 


Aquamarine,  392 
Aragonite,  332,  63,  64 
Argentine,  335 
Argentite,  297 
Arsenic,  270 
Arsenopyrite,  214,  64 
Asbestus,  390,  420,  371 
Asparagus  stone,  330 
Asphaltum,  364 
Atacamite,  289 
Augite,  386 
Autunite,  277,  156 
Aventurine,  374 
Axinite,  408,  25 
Azurite,  290 

Balas  ruby,  341,  342 
Barite,  319,  34,  16 
Barytocalcite,  321 
Bastite,  385 
Bauxite  , 
Beryl,  391,  50,  137,  189 
Biotite,  418,  371 
Bismite,  269 
Bismuth,  267 
',  Bismuth  ochre,  269 
Bismuthinite,  268 
Bismutite,  269 
Bitumens,  364 
Black  diamond,  367 

hematite,  231 

jack,   242 

lead,  368 

mica,  418 

oxide  of  copper,  289 

oxide  of  manganese,  229 
Blende,  242 
Bloodstone,  375 
Blue  carbonate  of  copper,   290 

iron  earth,  223 
438 


INDEX   TO  MINERALS. 


439 


Blue  stone,  370 

Chili  saltpetre,  314 

vitriol,  289 

China  clay,  422 

Bog  iron  ore,  221,  222 

Chloanthite,  236 

manganese,  231 

Chlorite,  419 

Boracite,  359 

Chondrodite,  409 

Borax,  356 

Chromic  iron,  224 

Bornite,  284 

Chromite,  224 

Boronatrocalcite,  357 

Chrysoberyl,  353 

Bort,  367 

Chrysocolla,  291 

Bournonite,  258 

Chrysolite,  398 

Braunite,  228 

Chrysoprase,  375 

Brimstone,   360 

Chrysotile,  420 

Brittle  silver  ore,  300 

Cinnabar,  294 

Brochantite,  289 

Clausthalite,  259 

Bromargyrite,  302 

Clay,  422,  371 

Bromyrite,  302 

Clay  ironstone,  219 

Bronze  mica,  419 

Clinochlore,  419 

Bronzite,  384 

Coal,  mineral,  366 

Brookite,  252 

Cobalt  glance,  234 

Brown  clay  ironstone,  222 

pyrites,  233 

hematite,  221 

Cobaltite,  234 

Brucite,  340 

Colemanite,  357 

Bytownite,  383 

Columbite,  225 

Copal,  365 

Calamine,  246,  244,  136 

Copiapite,  222 

Calaverite,  306 

Copper,  282,  134,  135 

Calc  spar,  333 

Copper  glance,  283 

Calcite,  333,  17,  44,  65,  132,  143,  159 

nickel,  239 

Calomel,  294 

pyrites,  284 

Cancrinite,  395 

uranite,  277 

Capillary  pyrites,  238 

vitriol,  289 

Carbonado,  367 

Cordierite,  394 

Carnallite,  310 

Corundum,  346,  45,  132 

Carnelian,  375 

Crocidolite,  391 

Carnotite,  277 

Crocoite,  263 

Caryocerite,  252 

Cryolite,  346 

Cassiterite,  249,  40,  64 

Cuprite,  288 

Cat's-eye,  354,  374 

Cyanite,  392,  25,  138 

Celestite,  321 

Cymophane,  354 

Cerargyrite,  301 

Cerussite,  262 

Dammar,  365 

Ceylonite,  342 

Damourite,  418 

Chabazite,  414 

Dark  ruby  silver,  299 

Chalcanthite,  289 

Datolite,  405 

Chalcedony,  372,  375 

Delessite,  420 

Chalcocite,  283 

Descloizite,  265 

Chalcopyrite,  284 

Desmine,  414 

Chalk,  335 

Diallage,  386 

Chesterlite,  381 

Diamond,  366,  156 

Chiastolite,  404,  133 

Diaspore,  349 

440 


INDEX   TO  MINERALS. 


Dichroite,  394 

Glauberite,  314 

Diopside,  386 

Glaucophane,  390 

Dioptase,  292 

Goethite,  220 

Dog-tooth  spar,  335 

Gold,  304 

Dolomite,  335 

Gold  Telluride,  306 

Dry-bone,  244 

Goshenite,  392 

Goslarite,  243 

Edenite,  390 

Graphite,  368 

Eisstein,  346 

Gray  antimony,  273 

Elseolite,  395 

copper  ore,  286 

Elaterite,  364 

Greasy  quartz,   374 

Electric  calamine,  246 

Greenockite,  247 

Embolite,  302 

Green  carbonate  of  copper,  290 

Emerald,  391 

Grossularite,  397 

Emery,  346,  347 

Guano,  331 

Enargite,  286 

Gummite,  252 

Enstatite,  384 

Gypsum,  328,  12,  63,  178 

Epidote,  406 

Epsomite,  340 

Halite,  312 

Epsom  salt,  340 

Hausmannite,  229,  64 

Erythrite,  236 

Haiiynite,  395 

Euxenite,  252 

Heavy  spar,  319 

Hedenbergite,  386 

False  topaz,  374 

Heliotrope,  375 

Fayalite,  399 

Hematite,  217,  45,  140,  192 

Feather  ore,  259 

Hessite,  298 

Feldspar,  378,  371 

Heulandite,  414 

Fibrolite,  405 

Hiddenite,  317 

Fiorite,  377 

Hornblende,  390 

Ferruginous  quartz,  374 

Horn  silver,  301 

Fire  opal,  377 

mercury,  294 

Flint,  375 

Horse  flesh  ore,  284 

Flos  ferri,  332 

Hyacinth,  402 

Fluorite,  325,  156 

Hyalite,  377,  156 

Fluor  spar,  325 

Hyalosiderite,  399 

Fontainebleau  sandstone,  335 

Hydraulic  limestone,  335 

Fool's  gold,  210 

Hydrozincite,  244 

Franklinite,  217 

Hydrohematite,  220 

French  chalk,  421 

Hypersthene,  384 

Fullers  earth,  372 

Ice,  361 

Galena,  256 

Iceland  spar,  333,  335 

Galenite,  256 

Idocrase,  401 

Garnet,  396,  372 

Ilmenite,  219 

Garnierite,  240 

Indianite,  382 

Gay-Lussite,  315 

Infusorial  earth,  377,  37.. 

Geyserite,  377 

lodargyrite,  302 

Gibbsite,  351 

lodyrite,  302 

Gilsonitt    364 

lolite,  394,  175 

Glauber  salt,  314 

Iridosmine,  308 

INDEX   TO  MINERALS. 


Iron,  208. 

Manganblende,  228 

Iron  pyrites,  210 

Manganite,  230 

Isinglass,  417 

Manjak,  364 

Marble,  333,  335 

Jade,  390 

Marl,  335 

Jadeite,  386 

Marcasite,  212,  63 

Jamesonite,  259 

Martite,  219 

Jasper,  372,  375 

Mascagnite,  318 

Meerschaum,  422 

Kuinite,  310 

Melaconite,  289 

Kalinite,  311 

Melanterite,  223 

Kaolin,  422 

Melilite,  402 

Kaolinite,  422,  371 

Menaccanite,  219 

Kermesite,  275 

Mercury,  293 

Kidney  Ore,   140 

Mica,  416,  371 

Krennerite,  306 

Microcline,  380 

Kunzite,  317 

Milky  quartz,  374 

Kyanite,  392 

Millerite,  238 

Mimetite,  262 

Labradorite,  383 

Mineral  coal,  366 

Lapis  Lazuli,  396 

Minium,  259 

Lazurite,  396 

Mirabilite,  314 

Lead,  256 

Mispickel,  214 

Lepidolite.  317 

Misy,  222 

Leucite,  384 

Molybdenite,  278 

Leucopyrite,  215 

Molybdite,  278 

Libethenite,  289 

Monazite,  253 

Light  ruby  silver,  299 

Mundic,  209 

Lime  feldspar,  382 

Muscovite,  417,  371 

soda  feldspar,  383 

uranite,  277 

Native  antimony,  273 

Limestone,  333,  335 

arsenic,  270 

Limonite,  221 

boric  acid,  356 

Linarite,  260 

bismuth,  267 

Linnaeite,  233 

copper,  282 

Lithia  mica,  317 

gold,  304 

Lithographic  limestone,  335 

iron,  208 

Lodestone,  215 

lead,  256 

Lollingite,  215 

mercury,  293 

Loxoclase,  380 

platinum,  308 

silver,  296 

Mackintoshite,  252 

sulphur,  360 

Magnesian  limestone,  335 

tellurium,  361 

mica,  418 

ultramarine,  396 

Magnesite,  340 

vermilion,  294 

Magnetic  iron  ore,  215 

Natural  gas,  363 

pyrites,   209 

Natrolite,  416 

Magnetite,  215,  131,  133,  139                       Nmlle  zeolite,  416 

Malachite,  290                                              Nephelite,  395 

Malacolite,  386                                                     Nephrite,  390 

442 


INDEX   TO   MINERALS. 


Niccolite,  239 

Potash  feldspar,  378 

Nickel  bloom,  239 

mica,  417 

Nigrine,  251 

Prase,  375 

Nitre,  311 

Precious  opal,  377 

Noselite,  395 

garnet,  397 

Noumeite,  240 

Prehnite,  408,  140 

Priceite,  358 

Ochre,  red,  219 

Prochlorite,  419 

yellow,  222 

Proustite,  299 

Octahedrite,  252 

Psilomelane,  231 

Oligoclase,  383 

Purple  copper  ore,  284 

Oligoclase-albite,  383 

Pyrargyrite,  299 

Olivenite,  290 

Pyrite,  210,  66,  131,  148 

Olivine,  398 

Pyrochlore,  252 

Onyx,  335,  375 

Pyrolusite,  229 

Opal,  376 

Pyromorphite,  260 

jasper,  377 

Pyrope,  397 

Orangite,  254 

Pyrophyllite,  423 

Orpiment,  271 

Pyroxene,  385 

Orthoclase,  378,  29,  64 

Pyrrhotite,  209 

Osteolite,  331 

Ozocerite,  365 

Quartz,  372,  65,  66,  131,  171 

Pandermite,  358 

Realgar,  271 

Pearl  sinter,  377 

Red  antimony,  275 

Pearl  spar,  335 

hematite,  219 

Pectolite,  387,  135 

iron  ore,  217 

Pencil-stone,  423 

ochre,  219 

Pentlandite,  238 

oxide  of  copper,  288 

Peridot,  398 

silver  ore,  299 

Pericline,  382 

zinc  ore,  243 

Perthite,  381 

Rensselaerite,  421 

Petalite,  378 

Rhodochrosite,  231 

Petroleum,  363 

Rhodonite,  387 

Pharmacolite,  331 

Rhyacolite,  380 

Phenacite,  399 

Ripidolite,  419 

Phlogopite,  419 

Rock  crystal,  374 

Phosgenite,  263 

gypsum,  329 

Phosphate  rock,  330,  331 

meal,  335 

Phosphorite,  331 

salt,  312 

Picotite,  342 

Rose  quartz,  374 

Piedmontite,  408 

Ruby,  340,  347 

Pitchblende,  276 

copper,  288 

Plagioclase,  381 

spinel,  342 

Plasma,  375 

silver,  299 

Platinum,  308 

Rutile,  251,  133 

Plumbago,  368 

Plumbocalcite,  335 

Sal  ammoniac,  318 

Polybasite,  301 

Salt,  312 

Potash  alum,  311                                                   Saltpetre,  311 

IXDEX   TO   MINERALS. 


443 


Sanidin,  380 
Sapphire,  346,  347 
Sard,  375 
Sardonyx,  375 
Sassolite,  356 
Satin-spar,  329,  335 
Scapolite,  400 
Scheelite,  339 
Schorl,  409 
Selenite,  328,  329 
Semi  opal,  377 
Senarmontite,  275 
Sepiolite,  422 
Serpentine,  420,  138,  371 


Siliceous  sinter,  377 
Sillimanite,  405 
Silver,  296 
Silver  glance,  297 
Smaltite,  235 
Smithsonite,  244 
Smoky  quartz,  374 
Snow,  361 
Soapstone,  421,  370 
Soda  feldspar,  382 

lime  feldspar,  383 
Soda  nitre,  314 
Sodalite,  395 
Spartaite,  335 
Spathic  ore,  223 
Specular  iron,  217,  219 
Sperrylite,  308 
Spessartite,  397 
Sphalerite,  242 
Sphene,  424 
Spinel,  341,  66 
Spodumene,  316 
Stalactite,  335 
Stalagmite,  335 
Stannite,  249 
Stassfurtite,  359 
Staurolite,  410,  64 
Steatite,  421 
Stephanite,  300 
Stibnite,  273 
Stilbite,  4H 
Stream  tin,  249,  2$O 
Stromeyerite,  298 
Strontianite,  323 
Succinite,  365 


Sulphur,  360,  197 
Sylvanite,  306 
Sylvite,  310 

Talc,  421,  370 
Tantalite,  225 
Tellurium,  361 
Tennantite,  288 
Tenorite,  289 
Tetradymite,  268 
Tetrahedrite,  286 
Thenardite,  314 
Thomsonite,  416 
Thorite,  254 
Thulite,  406 
Tin  stone,  249,  250 
Tin  pyrites,  249 
Tinkal,  356 
Titanic  iron  ore,  219 
Titanite,  424 
Topaz,  403 
Torbernite,  277 
Touchstone,  375 
Tourmaline,  409,  48,  132 
Travertine,  335 
Tremolite,  390 
Tridymite,  376 
Tripolite,  377 
Trona,  315 
Troostite,  245 
Tscheffkinite,  252 
Turgite,  220 
Turquois,  352 

Ulexite,  357 
Umber,  222 
Uralite,  391 
Uraninite,  276 
Urao,  315 
Uvarovite,  397 

Valentinite,  275 
Vanadinite,  264 
Vesuvianite,  401,  39 
Vivianite,  223 

Wad,  231 
Water,  361 
Wavellite,  352 
Wernerite,  400 


444 


INDEX   TO  MINERALS. 


White  iron  pyrites,  212 
lead  ore,  262 
mica,  417 

Willemite,  245 

Witherite,  320 

Wolframite,  225 

Wollastonite,  387 

Wood-opal,  377 

Wood-tin,  250 

Wulfenite,  265,  148 

Yellow  copper  ore,  284 


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quartz,  374 
Yttrialite,  252 

Zinc  blende,  242 
vitriol,  242 
bloom,  244 

Zincite,  243 

Zircon,  402,  12,  39 

Zirkelite,  252 

Zoisite,  406 


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Books  and  Pamphlets  on  Mineralogy 

Characters  of  Crystals.    By  ALFRED  J.  MOSES.    Pp.  211,  321  figures.    Price,  $2.00 
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Rapid  Qualitative  Examination  of  Mineral  Substances.     By  ALFRED  J. 

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STRUCTURAL 


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WITH  52  FULL  PAGE  PLATES  AND 
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OOISTTEitTTS- 

CHAP.  I-TI— Rock-forming  Minerals. 
CHAP.  II1-IV-V— Rock. 
CHAP.  VI— Fossils. 

CHAP.  VII— Stratification  and  Formation  of  Rock-Beds. 

CHAP.  VIII— Concretionary  and  Secretionary  Structures. 
CHAP.  IX— Inclination  and  Curvature  of  Strata. 
CHAP.  X— Joints. 

CHAP.  XI— Faults  or  Dislocations. 

CHAP.  XII— Structures  Resulting-  from   Denu- 
dations. 

CHAP.  XIII-XIV.— Eruptive  Rocks:  Mode  of  their  Occurrence. 
CHAP.  XV. — Alternation  and  Metamorphisin. 
CHAP.  XVI-XVII— Ore-Formations. 

CHAP.  XVIII-XIX-XX— Geological  Surveving. 
CHAP.  XXI— Geological  Maps  and  Sections. 

CHAP.    XXII-XXIII— Economic  Aspects    of  Geological 

Structure. 
CHAP.— XXIV— Soils  and  Sub-Soils. 

CHAP.  XXV— Geological     Structure     and    Surface 

Features. 
Appendices.    Index. 


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